Soften onions with olive oil in a Dutch oven on low heat. Add and soften capsicum and garlic. Brown sausages with oregano then a splash of Worcestershire sauce.
Add passata, stock, dried pasta, sugar, salt and pepper. Bring up to boil.
Bake for 15 minutes then scatter mozzarella cheese all over. Return to the oven and bake until cheese is lightly golden.