Cut the shallots into fine rings and fry them in a large saucepan with a little oil or fat. Add the bacon cubes and fry briefly. Add the thawed spinach and heat. Pour the milk on top and let it simmer.
Dice the feta cheese and add it. Simmer, stirring, until the cheese is completely melted. Season to taste with salt and pepper.
Cook the pasta in boiling salted water, then drain. Distribute on deep plates and pour the sauce over them.