In a bowl, whisk together the eggs, cottage cheese and grated cheese. Add the oregano and a little salt and pepper for taste. Place the spinach, chorizo ​​and tomatoes in a greased baking dish. Pour over the egg mixture. Place the baking dish in the oven for about 25 minutes until the frittata has a nice colour. In the oven, the frittata rises a bit, but when you take it out, it collapses again. When it has cooled down, scatter the basil leaves over it.