Tip the lentils into a bowl and cover with cold water. Set aside.
Prepare the veg
Trim and roughly chop the onion, celery root, leek, celery, and mushrooms.
Peel the garlic.
Add the onion and celery root to the processor with half the mushrooms. Pulse until you have rough dice, then tip into a bowl.
Add the onion, leek, celery, garlic, and parsley to the processor with the rest of the mushrooms.
Pulse to chop, then add to the bowl with the onion and celery root.
Continue in batches until all the vegetables are chopped. Stir to combine.
Cook the veg
Place the pan over medium heat and add the olive oil.
Once the oil is hot, add the chopped veg, stir, cover, and cook over low heat for 20 minutes, stirring occasionally, then remove the lid.
Add the tomato paste and balsamic vinegar, scraping the bottom of the pan to get any tasty bits of caramelized veg off the bottom.
Add the wine (if using), stock, chopped tomatoes, cinnamon sticks, bay leaves, and thyme. Season generously. Simmer for 30 minutes.
Drain the lentils and add them to the pan, cover and cook for another 10-15 minutes, until the lentils are cooked.
Taste and adjust the seasoning, adding more balsamic vinegar if you want more sweetness and acidity. Remove the cinnamon sticks and bay leaves and you’re good to go!
Store
Allow the Bolognese to cool and then portion up and freeze lying flat as this makes it super-quick to defrost when you want a quick supper.