Add the olive oil to a large pan or braiser with straight sides. Fry the onion till translucent, but not browned. * See note
Add the garlic and fry for another 30 seconds till fragrant.
Add the bell peppers and mushrooms and stir-fry for another 2 to 3 minutes.
Add the chilli flakes, origanum, stock, tinned tomatoes, water and tomato paste and mix.
Add the spaghetti and make sure it is covered with the liquid. Season to taste.
Cook for 8 - 10 minutes on medium heat, stirring often. You can also turn the pasta with tongs as Martha Steward suggests.
After ten minutes most of the liquid should have cooked away. Add the spinach and basil leaves and check the seasoning.
Serve immediately with grated parmesan or another type of hard cheese.