Pour 200ml milk and 200ml water into a large pan. Add the bay leaf and thyme leaves. Set over a medium heat and gently warm till steaming hot.
While the milk heats, peel and thinly slice the red onion. Tip into a bowl and grate in half the nutmeg. Add a large pinch of salt and pepper.
Coarsely grate half the chunk of cheddar. Crumble ½ the pack of Perl Las. Snap the spaghetti in half.
Add the spaghetti to the pan and push down into the warm milk. Add the onion and the cheeses. Turn up the heat and cook till the mix just starts to simmer.
Turn the heat down, put the lid on the pan and simmer for 20-25 mins till the spaghetti is tender and the sauce has reduced till it coats the spaghetti. Give it a stir every so often to mix the sauce. The blue cheese will make it look a little curdled, but keep gently simmering and the sauce will come together.
While the spaghetti simmers, quarter the cherry tomatoes. Pop them in a bowl. Add 2 tsp olive oil and a good pinch of salt and pepper. Toss to mix. Set aside.
Add the spinach to the pan and toss it through the cheesy spaghetti to wilt it. Taste and season the spaghetti. Spoon into warm bowls and grate over a little more nutmeg to taste. Serve with the tomato salad.