Heat the olive oil in a large saucepan. Dice the onion and garlic and sauté them until translucent. Add the tomato paste and fry briefly. Pour in the milk, cream and chunky tomatoes and bring to the boil. Season well with salt and pepper.
Then add the noodles and cover and cook for about 10 minutes (depending on the variety used) over light to medium heat. Stir regularly so that nothing cakes.
While the pasta is cooking, drain the peas and mushrooms, dice the ham and slice the mozzarella.
At the end of the cooking time - the pasta should still have a bit of bite - remove the pan from the heat and fold in the peas, mushrooms and ham. Transfer everything into a greased baking dish.
Cover the casserole with the mozzarella and bake in the oven for about 10-15 minutes until the cheese is golden brown.