Bake the sausage on the grill, medium brazier, 40cm from the ember and do not pierce the sausage. Also put the onion and tomatoes to grill;
Take the pre-cooked potato, and with the fork, mash it.
In a large pan, place half the butter, a drizzle of olive oil, the chopped onion, chopped garlic, sauté.
Add the potato and mix well. Add the milk to cook together (the amount of milk depends on whether you want to make it more or less creamy). A bit of salt. Finish with the rest of the butter. Reserve;
Remove the sausage and the grilled onions and tomatoes;
Cut the sausage into small cubes and place in a refractory.
Add the chopped tomato, chopped onion, chopped parsley. Mix it all up;
In one form, make a layer of puree.
Put the seasoned sausage and spread it in the form.
Make another layer of puree to cover. Model, cover with the mozzarella and finish with olive oil. - Take it to the oven for fixings at 230 degrees for 15 minutes. It's ready to serve.
@luana_21