Preheat the oven at 375 º. Cook the pasta al dente in a large pot of salted water. In the meantime prepare the béchamel sauce. Add the mozzarella, the peas and the ham.
When pasta is done, drain and put back in the cooking pot. Add the béchamel sauce and stir well and put into a large Pyrex baking pan and place in the hot oven for 30 minutes or until the top is starting to brown.