1. Peel and finely chop the onion. Trim the carrots, then peel and dice them. Trim the dry ends off the celery sticks and dice them, too. Rinse the mushrooms and slice or tear them into small pieces.
2. Warm a large pan over a medium-low heat and add 1 tbsp olive oil and the chopped veg. Season with a pinch of salt and pepper. Pop a lid on the pan, or use a baking tray if you don’t have a lid. Fry the veg, stirring often, for 10 mins till the veg are glossy and starting to soften.
3. While the veg fry, peel and crush or grate 2 of the garlic cloves (save the rest for later). Pick the rosemary leaves off their woody stalks and roughly chop them. Stir the garlic and rosemary into the veg. Cook and stir for 2 mins till the pan smells aromatic.
4. Pour in the passata. Drain the lentils, then add them to the pan. Add a pinch more salt and pepper, and a pinch of sugar if you like. Give it all a good stir, then bring to the boil. When the sauce is boiling, turn the heat down, pop the lid back on and simmer for 20 mins, stirring every so often, till the sauce has started to thicken.
5. Meanwhile, put a large pan of salted water on to boil. When the sauce has 10 mins cooking time left, check the pan of water – it should be boiling. Add the spaghetti and simmer for 10-12 mins till it’s cooked but not too soft. It should still have a little bounce and bite to it.
6. While the spaghetti cooks, peel and finely chop the remaining 2 garlic cloves. Scoop them into a bowl. Finely chop the parsley leaves and stalks and add to the garlic. Finely grate in the lemon zest and squeeze in the juice from half the lemon. Add 1 tbsp olive oil and a pinch of salt and pepper. Stir to mix. This is your gremolata.
7. The bolognese sauce should have thickened and the lentils should be tender. Taste the sauce and add a pinch of salt, pepper, sugar, or a squeeze of lemon
juice, if you think it needs it. Drain the spaghetti and divide between four warm bowls or plates. Top with the bolognese sauce, spoon over the gremolata and scatter over the pine nuts to serve.
8. Love Your Leftovers
The spaghetti bolognese will keep for up to 3 days in the fridge in airtight tubs or can be frozen for up to 3 months. Mix the pasta and sauce together, then divide between the tubs and seal. Reheat in the microwave or on the hob, with an extra splash of water or stock, till piping hot.