Dice the chorizo and courgette into 5mm cubes. Place the chorizo in the cold frying pan and leave the courgettes to one side. Turn the heat to medium, so that the chorizo cooks in its own, delicious, fat.
Once the chorizo is crispy, remove and put to one side. Add at least one tablespoon of oil (any will do, including any leftover pork fat you might have from a roast). Put the diced courgette into the pan and cook slowly.
With the courgettes in the pan, put your pasta on to cook. Put the timer on for 4 minutes fewer than the packet cooking time.
Before you strain the pasta, dip the jug or mug into the pot and save at least 50ml of pasta water. Then strain away.
When your courgettes are soft, chop/crush/grate your garlic. Turn the heat up a little, and stir the garlic through for a minute, until you can smell it. Return the chorizo to the pan, and then pour the pasta into the pan.
Stir everything round, and splash on a little pasta water to help to combine everything (this is why you undercooked the pasta). Taste, season, and add a drop more water if you like.
Serve.