Peel and finely chop the onion. Trim the carrots, then peel and dice them. Trim the dry ends off the celery and dice them, too. Rinse the mushrooms and slice or tear them into small pieces.

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 and 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.

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 is aromatic.

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.

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 8-10 mins till it’s cooked but not too soft, it should still have a little bounce and bite to it.

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.

The bolognese sauce should have thickened and the lentils should be tender. Taste the sauce and add a pinch more salt, pepper, sugar, or a squeeze of lemon juice, if you think it needs it. Drain the spaghetti and divide between four warm bowls of plates. Top with the bolognese sauce, spoon over the gremolata and scatter over the pine nuts to serve

[BOX] Food Waste Heroes If you’re making vegetable stock, add the peelings from your onion, carrots and garlic along with the celery trimmings and woody rosemary sprigs. Add a mix of onions, carrots and celery, with a few pot herbs, such as bay or parsley. Cover with water and simmer for 45 mins to make a veg stock. Strain and store in the fridge for up to 3 days or freeze for up to 3 months.

Love Your Leftovers^ The bolognese will keep for up to 3 days in the fridge in airtight tubs. Divide the bolognese between the tubs and seal. Reheat in the microwave or on the hob, with an extra splash of water or stock, till piping hot.The pasta will taste better cooked to order.