Place a heavy-based casserole dish, deep frying pan or large pan on a medium heat and warm it for 2 mins. Add ½ tbsp oil and the pork mince. Fry for 8 mins, stirring every so often till the pork mince has browned all over.
While the mince fries, peel and finely chop the onion. Peel and dice the carrot. Trim the dry ends off the celery stick, then finely slice the celery. Peel and finely chop the garlic.
Stir the chopped veg into the mince. Add a pinch of salt and pepper and sizzle for another 5 mins, till the veg start to soften.
Stir in the garlic. Crumble in the chicken stock cube. Stir to mix. Drop in the bay leaf and most of the thyme (keep a sprig back for garnishing). Tip in the tin of chopped tomatoes. Pour in 800ml boiling water. Stir to mix well.
Lay the spaghetti in the pan. Pop on a lid (or use a baking tray if you don’t have a lid). Bring the pan up to the boil, then turn the heat down and simmer for 25-30 mins. Stir 2 or 3 times to mix the spaghetti in with the sauce.
While the spaghetti simmers, toss the rocket with 2 tsp olive oil and a pinch of salt and pepper.
After 25 mins, check the spaghetti. It should be tender but still with a little bite, and the sauce should have thickened. Taste the sauce and add a pinch more salt and pepper if you think it needs it.
Heap the spaghetti and sauce up on warm plates, discarding the thyme sprigs. Serve with the rocket, garnished with a few fresh thyme leaves.