Mash the potatoes. Use a potato ricer if possible or mash the potato then pass through a sieve. This gets rid of any lumps. Put in a mixing bowl.
Sieve the flour into the bowl of potato. Add the beaten egg, salt and pepper. Mix with a spoon so it forms a dough.
Flour the work surface and your hands and knead for about 5 minutes. Keep adding extra flour as necessary to stop it sticking.
Divide the dough into four. Divide each in half again then roll out into a long sausage about one centimetre wide. Slice into gnocchi about one centimetre long each. Repeat with all the dough. If only serving 2 people, put half the gnocchi in the freezer. Let them freeze individually on a lined baking tray, then put them all together in a bag when they are frozen.
Put a saucepan of water on to boil. At the same time heat a wok. When hot, add the chorizo, stir, cooking on both sides. The chorizo should release red oil. Add the garlic and tomatoes. Keep stirring so it doesn't burn.
Add the gnocchi to the saucepan of boiling water. Boil for about 3 minutes. They should all rise to the surface.
Drain the gnocchi and add to the wok. Stir so all the gnocchi are coated in the sauce. Serve with grated parmesan.
Nutritional information is approximate and a guideline only.