Step 1

Place the onion, carrot, celery and garlic in a food processor. Process until finely chopped. Set aside.

Step 2

Heat oil in a large frying pan over medium heat. When hot, add sausages and cook for 2-3 minutes until golden brown. Transfer to a plate and set aside.

Step 3

Add vegetables to the pan and cook over medium heat for about 5 minutes until softened. Add mushrooms and cook for a further minute. Add the wine, tomatoes, pesto, sugar and oregano. Season well with salt and pepper. Bring to the boil, then reduce heat to low, cover and cook for 15 minutes. Remove lid, add sausages and cook for 15 minutes or until sauce is thick. Stir in the basil.

Step 4

Meanwhile, bring 1 litre of water to the boil. Reduce heat to low and add polenta in a slow, steady stream. Cook for 6-7 minutes, stirring constantly. Remove from heat and stir in butter and half the parmesan. Season well. Place polenta on each plate, top with casserole and garnish with basil. Serve with remaining parmesan.