"It's a very reflective new year for me. I don't find the Gregorian New Year as spiritually fulfilling as Rosh Hashanah and Yom Kippur. I feel like my brain is really geared towards a Jewish calendar."

So says Mayim Bialik, the actress who shot to fame a few years ago as Amy Farrah Fowler, straight- talking, slightly awkward and much-loved girlfriend of super-geek Sheldon Cooper in blockbuster sitcom The Big Bang Theory.

You might remember her aged 13 as the young Bette Midler in the 1988 film, Beaches. I've been a fan since she first graced our TVs in 1990 as the hat-wearing, handstand-doing Blossom in the show of the same name.

Blossom was the girl I wanted as my friend and the girl I wanted to be. She tap-danced on a piano in the programme's opening credits, had a best friend called Six, an attractive older brother, and the best lines. She was funny, clever and familiar in a way that other TV stars weren't.

When Bialik first answers the phone for our interview I'm expecting an agent or PR to transfer me through so I get a shock to hear her unmistakable voice. The fan-girl in me starts to rise to the surface and I have to bat her away and remember that I'm a grown-up.

Quickly I feel at ease. Bialik is just as friendly, nice and clever as I imagined all those years ago, and she chats - in fast, long sentences - about Jewish stuff, just like we've known each other for years.

This year she'll be celebrating the holidays with her children, mother and ex-husband as usual.

"We have a home cooked meal. My ex and I do the cooking, my mum chips in and we just like to be together. We like leftovers after synagogue the next day! We try and do tashlich if we can but it's kind of hard; there were years when we weren't driving and there were years when we were driving just to go to synagogue, so we try and keep it as simple as we can."

And this year - as every year - she will be blowing the shofar.

"I was a trumpet player in my youth [Bialik also plays bass guitar and the piano] and the rabbi at the synagogue I grew up in had seen me play the trumpet on a talk show after Beaches came out when I was 13 and he said 'Have you ever blown the shofar?' I've done it in just about every community that I've lived in since."

Bialik has scooped up acting awards and nominations, as a child and an adult, but she has other impressive achievements away from the world of show business. She studied Neuroscience and Hebrew and Jewish studies at UCLA and took a PhD in an area of neuroscience so specialised that the name of her dissertation, something to do with Obsessive Compulsive Disorder, makes my head spin - it's pure Big Bang Theory. She then taught neuroscience to home-schooled teenagers. In fact, she would still be nourishing young minds, if it were not for one crucial detail. "I actually was running out of health insurance is the true story," she tells me. "Life is funny."

"I figured I've never acted as an adult and if I can just get a little health insurance it will make life easier. I had a young baby and toddler so I just started auditioning."

She had never seen The Big Bang Theory. "I had heard of it and I thought it was a game show! And I auditioned and my life really changed."

Bialik, 40, regrets little about her 12-year break from show business.

"I love seeing the world as a scientist; I love my training I feel it makes me a really well-rounded person."

Does her scientific background help when playing Amy the earnest neurobiologist? Bialik says no, essentially all you need to be a good actor is to, well, be a good actor.

"As actors we're paid to pretend like we're all sorts of people and things that we have no experience with." She points out that her Big Bang colleagues "- and most actors that you know in the world- are not scientists, and they do a pretty good job."

Bialik is also a prolific writer. She's written three books: a vegan recipe book - she became vegan at 19 - and two non-fiction books drawing on her neuroscience background. Her new book, coming out in the spring, is aimed at young girls. Called Girling Up: How to be Strong, Smart and Spectacular, Bialik describes it as "an exploration of everything about being female". Using her experience of growing up in the public eye and also being a "late bloomer" the book covers anatomy, dating, eating disorders - how to deal with "the hard stuff life throws at you."

She blogs regularly, both for Jewish parenting site Kveller and her own blog, Grok Nation. "I started blogging when a lot of mums were," she says.

"Kveller was one of the only sites that was telling it like it was and not sugar-coating parenting and that really appealed to me."

Now she mostly posts on Grok Nation. As well as covering parenting, women, culture and faith, it's the platform for Bialik's high profile support for the National Alliance on Mental Illness.

When comedian Robin Williams died she spoke of her sadness, and said it hit hard, "because there are people in my life who suffer from the kind of mental illness that Robin Williams suffered from." She's not forthcoming with details, but tells me that she's used the NAMI's services and "wanted to give back." Her emphasis is on removing the stigma that often comes with asking for help.

Her family story is a very Jewish one. "Three of my four grandparents were immigrants to America; I'm half Polish, a quarter Hungarian and a quarter Ukrainian. My grandmother came to America as an orphan just before the war. Half of her siblings died in the Holocaust and the rest were reunited here." She's also related to Israel's national poet, Hayim Nahman Bialik.

Her mother was raised in an Orthodox household while her father, was "more assimilated".

Bialik herself had a Reform upbringing - "my parents had pulled away from traditional Judaism" - sprinkled with her mother's "leftovers from Orthodoxy," such as having two sets of dishes, "but no one really explained why." She became more observant in her early teens.

I've been aware of Bialik as a proponent for Orthodox Judaism - she has written about her faith and been outspoken about modesty, saying in 2013, "As a person who spends much of my life as a public person being observed, judged, and picked apart for how I look, I have come more and more to appreciate the healthy sense of protection that tznius [Jewish modesty] provides me" - but now she tells me she's "never waved the flag of Orthodoxy.

"A lot of people are using the term 'post-denominational' which in some ways is really vague, but in some ways is really descriptive of the fact that I can pray in a lot of different areas. I prefer to pray in a modern Orthodox setting, but there are times when I pray with mixed seating [or] go to Reform synagogues.

"Because of the way my schedule and life works I don't always get off for every single holiday that I would like to observe but I believe in the structure of Jewish law and I believe in the expansiveness and flexibility of the Jewish people."

She says her Judaism is "inescapable," something that has given her great strength in trying times.

Her father died on the penultimate day of Pesach last year. He had been in a hospice for two months, so although Bialik "had months to process and love and grieve and rage at God and all of that," as she wrote on Kveller at the time, she says now that her grief is "pervasive" and "complicated".

Her Judaism "absolutely" helped her deal with her loss. "I don't think that I could have processed my father's death without the structure - everything was so critical to me moving through a complicated grief," she tells me. "I took tremendous comfort in saying kaddish; I did it for a year."

Family is important to Bialik. She has two children - Miles, 11 and Frederick, eight (she offers to tell me their silly nicknames but then thinks better of it) - and although she has been divorced from their father for three years, they co-parent very closely. Bialik's ex was not Jewish when they met; he converted to Judaism before they got married (and "still considers himself to be Jewish" post-divorce) while his mother also converted after he and Bialik wed.

Bialik is protective of her boys. They are home-schooled and have never seen The Big Bang Theory as Bialik doesn't "consider [it] a show for them."

Miles "likes performing a lot but the lens they see acting through is very different. I thought I wanted to be an actress because I liked performing when I was young but they see a whole different side of it."

So is their understanding of acting more realistic than hers was? She laughs at the word 'realistic'. "The fact is most actors don't make a living as an actor so the fact that they see 'Oh my mum's an actor and that's her living', that's actually very unrealistic."

Bialik repeats throughout the interview that she is "grateful" to have such a successful acting career but has also written in the past that "a lead role has never happened for me". I say I'm surprised at this confession because in Blossom she played the titular character in a show that ran for five years.

"I was talking more about the notion of what leading ladies look like in Hollywood and character actresses," she clarifies. "There tends to be a look for leading ladies, we're seeing more quirky options for females but character actresses, we do different things in the acting world."

Is she happy being a 'character actress' rather than a 'leading lady'?

She pauses before answering. "I don't know. I mean it's kind of like saying are you happy with what you look like and how you present yourself?

"You are who you are, you sound the way you sound, so it's really about having realistic expectations of where you fit in to whatever career you're doing."

And with that in mind, does she have a favourite role? "Not really," she laughs. "I'm a happy product of whatever auditions come my way and whatever people want to cast me in. Playing Amy's really fun because of where I'm at in my life but all my characters are special to me in some way."

And talking of being realistic Bialik brings me back to earth with a bang. She's no pampered star, just a hard-working actress.

"I do have to go to work; that's what I'm doing next," she says as we close the conversation, in characteristically blunt Amy Farrah Fowler style.

But again, it's more like ending a conversation with a friend. No formal goodbyes, or professional requests to fact-check the quotes I might use. Just a casual "Oh I've got to go but it's great talking to you".

I still can't quite believe I spoke to Blossom/Amy and that we chatted about Rosh Hashanah, money troubles and leftovers – but do know that I'm an even bigger Mayim Bialik fan now than when I started.