Tuna and mushroom pasta

Ingredients:

450g (16 ounces) can tuna
1 large onion
90g (3 ounces) butter
90g (3 ounces) button mushrooms
300ml carton cream
2 tablespoons tomato paste
Salt
Pepper
1 tablespoon chopped parsley

Preparation:

Melt butter in pan. Add peeled and finely chopped onion and drained tuna to pan, stir over medium heat until onion is just tender.
Chop mushrooms in half, add to pan, toss lightly. Stir in cream, tomato paste, season with salt and pepper.
Bring sauce to boil, remove from heat immediately. Stir in chopped parsley.