Bring a medium saucepan of salted water to the boil for the spaghetti. Finely chop the capsicum. Quarter the carrot lengthwise and thinly slice. Coarsely chop the parsley leaves, discarding the stems. Using a small sharp knife, make a shallow cut along the length of each sausage, then peel off and discard the casings. Crumble the sausages into small chunks.
Step 2 — Start sauce
Heat 2 tsp olive oil in a medium deep frypan over medium-high heat. Cook the sausage, breaking up the lumps with a spoon, for 8 mins or until browned. Remove from the pan. Heat 2 tsp olive oil in the same pan. Cook the capsicum and carrot, stirring occasionally, for 4-5 mins until softened.
Step 3 — Cook spaghetti
Meanwhile, add three-quarters of the spaghetti* to the pan of boiling water (if you're tempted to throw in all the spaghetti, just note the dish won't be as saucy). Cook, stirring occasionally, for 12 mins or until al dente. Reserve 80ml (⅓ cup) cooking water, then drain the spaghetti.
Step 4 — Add sausage
Add 1 tsp dried oregano* and half the chilli flakes* (you can omit the chilli if preferred) to the vegetables and cook, stirring, for 1 min or until fragrant. Add the sausage and cook, stirring, for 1 min or until combined.
Step 5 — Finish sauce
Stir in the tomato passata and half the cream* and bring to a simmer. Reduce the heat to medium and cook, stirring occasionally, for 2-3 mins until slightly reduced.
Step 6 — Get ready to serve
Add the spaghetti to the sauce and stir to coat. Gradually add the reserved cooking water, stirring constantly, until the sauce coats the spaghetti and looks slightly glossy. Taste, then season with salt and pepper. Divide the spaghetti among bowls. Scatter with the parsley to serve.