These letters were filled with love and passion, as well as anger and stress.
They had been written in 1960 by Marisa and her husband, Pietro, when the couple was separated for seven months.
Pietro had moved from Italy to Melbourne to work as a chef for Mario Vigono at Mario's in Exhibition Street. The correspondence is from this time, when Marisa and their eldest daughter were still in Italy - bambino Grossi had not yet entered the world.
Grossi had his parents' letters translated to English so he could understand the emotion they portrayed. They impressed upon him how big a deal it is for someone to uplift their life and start over in a new land.
"I thought there's a huge story in this and it's about trying to bring things with you to the new place that remind you a little bit of home," says the celebrated Australian chef.
"The things that you can carry are the things like your passions, your beliefs, your culture and your recipes, and your stories.
"You kind of start to understand the psyche of wanting that little block of land and growing the vegetables and cooking beautiful food and creating an environment; you're adapting into your new home but bringing bits of your old one with you."
All of this led to Grossi penning his latest cookbook, Recipes from My Mother's Kitchen. His previous titles are Grossi Florentino (2007) co-authored with Jan McGuinness, and My Italian Heart (2011).
Excerpts from the letters feature throughout the pages of his new book, along with more than 100 recipes from the Grossi family table.
Among those are salted cod and artichokes; onion soup with bread dumplings; ricotta-filled cannelloni; and his mamma's jam tart.
Stephanie Alexander has also shared her mother's rabbit pie recipe, and comedian Jerry Lewis his favourite pasta dish.
Family stories from Italy and Australia feature throughout the pages and Grossi hopes readers will relate to them.
The Melbourne restauranteur finds it remarkable that in Australia people are learning to accept new cultures and helping to shape the country.
"I thought this was a wonderful story that needed to be told and why not tell it through the wonderful memories of my food growing up that my mum was cooking for me during those years?" Grossi tells AAP.
Grossi, who is owner and head chef of restaurant Grossi Florentino (Melbourne), and owner of Mirka (St Kilda), Merchant Osteria Veneta (Melbourne) and Grossi Trattoria (Bangkok), has fond memories of his childhood.
He describes the family home as warm and loving, where he was nurtured with beautiful food.
He helped his mother prepare meals and says she was a big inspiration.
"Certainly I draw from lots of other inspirations but my childhood background is probably one of the strongest, obviously, because it's what you become accustomed to."
His mother would recreate the recipes she learned in Italy but she also made an effort to adapt to her new home.
"One of the greatest things that strikes me in travelling is that in Australia we are just so good at having that multicultural kind of existence, that multicultural society, and we've allowed it to really flourish here," says Grossi, who is recognised as the country's leading authority on Italian cuisine.
Grossi's favourite meal of his mother's is a traditional lasagne, which he describes as "next to none". What makes it so special, he says, is the love she puts into the dish.
When Grossi cooks simple food for the home he says he makes sure it is well executed and has taken time to cook so there is depth of flavour.
His mother, he adds, loves to eat broth with pasta.
"...So if I was preparing something to start off with that I'd know she'd like I'd probably make a really beautifully intensely-flavoured broth with some lovely tortellini filled with maybe a veal filling or something like that."
For Grossi, food is an obsession and says it's an exciting industry to work in.
"I love the fact that we are privileged to be able to serve people that appreciate what we do.
"We get to work with magnificent produce, especially in Australia and that in itself is wonderful, and you get to work side by side with like-minded people that are very, very passionate about what they do and want to create something special."
He believes the industry is driven by the home cook and the family table.
As a good traditional Italian family, Sunday lunch was cherished in the Grossi household.
The family also made a tradition of preserving tomatoes in bottles every season so they could enjoy them year-round.
Melbourne-born Grossi tries to get back to Italy at least once a year.
Last June Grossi spent a month meeting suppliers and producers and he's planning to publish a cookbook about that culinary journey next year.
* Recipes from my Mother's Kitchen by Guy Grossi is published by Lantern, rrp $49.95.