Peel the carrots and onions and chop into 4 pieces. Add to a food processor fitted with the blades. Add the hazelnuts. Start the food processor and blitz until finely minced. Stop it from time to time and scrape the sides with a spatula.
Set a pot on medium heat and pour in the olive oil. After a minute add the carrot and onion mixture. Keep on medium heat and sweat for 5 minutes, stirring occasionally.
In the meantime, clean the button mushrooms, chop in half if large, and add to the food processor. There is no need to wash it in between. Blitz the mushrooms until finely minced. Aside, cut the dried porcini into small pieces.
Add both mushroom types to the pot and stir to distribute the heat. After 5 minutes, stir in the salt, white pepper and thyme. Add the white wine to deglaze, you may raise the heat a little bit, but make sure to keep a constant eye on it and stir around often.
When the wine has evaporated, lower the heat and pour in the tomato passata. Lastly, add 2 bay leaves to the sauce. Give it a good stir and bring to a boil. When it boils, lower the heat and let simmer with the lid on and just a slight crack to let steam evaporate. Simmer for one hour, stirring from time to time.
Notes
When using canned tomatoes (either if they are whole, chopped or passata) I always add a little water to the can or bottle to rinse and add the tomato water to my sauce. As far as I know, all grandmas in Italy do this, so we are not questioning it. I mean, we're just trying not to waste all the good tomatoes here, right?
Any leftovers can be kept refrigerated and airtight for up to 5 days, or in the freezer for up to 6 months.
The nutritional information provided is made with an online calculator and only meant to be used as a guideline.