Rinse the mushrooms and chop them roughly.

Melt butter in a saucepan and add mushrooms.

Fry for 5 minutes, stirring occasionally.

Stir in the flour and cook for 3 minutes.

Season with salt and pepper.

Meanwhile, cook the pasta shells in lots of boiling salted water for 10 minutes, or until tender but still firm.

Rinse in hot water and drain well.

Place in a warmed serving dish, and pour over mushroom sauce.