2. In a medium saucepan add the margarine and melt, remove from the heat and stir in the flour. Return to the heat and gradually add the soya milk until it is all incorporated.
3. Grate the cheddar cheese and add to the sauce. Heat until the cheese has melted and the sauce has a nice thick smooth consistency. Season to taste.
4. Meanwhile in a large pan of salted boiling water, cook the macaroni according to the instructions (usually 10-12mins). When the macaroni is cooked, stir into to the sauce along with the cauliflower and broccoli florets. Add mixture to a medium size-baking dish.
5. Mix the breadcrumbs with the grated Parmesan and the cayenne pepper and sprinkle on top of the dish. Cook for 35-40 minutes or until golden brown on top.