You start by cooking the gnocchi in a pan of boiling water for a couple of minutes (check the package for directions) until they float to the surface. Use a slotted spoon to take the gnocchi out of the water and strain the gnocchi until all of the liquid drains off. Don’t throw them into a hot frying pan immediately, because the water on the outside of the pasta will not allow the gnocchi to develop a nice, golden crust. Drain all the water (in a strainer) and add a drizzle of olive oil to a large frying pan over medium heat.
Put the gnocchi into the pan, and spread them around with the back of a spoon to create an even layer over the pan, this is very important for the crunchy crust. Let the gnocchi fry for a couple of minutes until they turn golden brown. Turn them gently with a spatula, and cook on the other side until brown and crispy. Take them out of the pan and set aside for later.
Cook the peas in a pan with boiling water for 4 minutes, drain and also set aside for later.
Heat 1 tablespoon oil in a large broiler-safe skillet over medium heat. Add onion and cook until brown which will take approximately 8 to 10 minutes. Take the sausages out of their casing and cut them in little pieces. Add the garlic to the pan and fry for a minute with the onion. Then add the sausage, salt and pepper and cook for 4 minutes while breaking up the sausage with a wooden spoon. Add spinach a handful at a time and cook, stirring, until wilted, this will take about 4 minutes.
Then add the canned tomatoes, the water (or the stock) and the dried herbs and spices. Taste and add seasoning when necessary. Mix well and add the fried gnocchi to the pan. Make sure there is enough liquid in the pan and if necessary add a dash of water. Top with mozzarella and Parmesan cheese and let it simmer for a while, until the cheese forms a melted gooey cheesy layer on the pasta. That takes about four minutes. In the meantime preheat the broiler of your oven.
Position a baking sheet in the upper third of oven. Broil until the cheese starts to brown, 3 to 5 minutes. This gives the cheese an irresistibly crusty crust. Remove from the oven, top with some chopped basil or oregano if desired.