Cook the pasta in a large saucepan of lightly salted boiling water for 10–12 minutes, or according to the packet instructions, until al dente.
Meanwhile, cook the broccoli and carrots in another large saucepan of boiling water for 5 minutes. Add the peas and red capsicum and cook for a further 3 minutes until all the vegetables are just tender. Drain and keep warm.
Melt the butter in a saucepan over a gentle heat. Add the garlic, cook for 2 minutes, then stir in the flour and cook for 1 minute, stirring occasionally.
Remove the pan from the heat and gradually stir in the milk and cream. Return the pan to the heat and bring to the boil, stirring continuously. Reduce the heat and simmer for 1–2 minutes, stirring occasionally, until the sauce thickens. Stir in the cheese until just melted and smooth, and season to taste with salt and pepper.
Drain the pasta well, then toss with the vegetables and the sauce. Transfer to a large dish and serve immediately.
To avoid waste, chop the broccoli stalks and toss them into a soup or casserole. Or thinly slice and blanch them for a salad.