Wash and drain the spinach.
Pour the bread cubes in a bowl with milk and egg.
Peel the onion, chop finely, roast in butter, add spinach and garlic and season with salt and pepper.
Add spinach and flour to the bread mixture and knead well. Form the spinach dumplings and boil them in salted water for about 15 minutes.
Remove the finished spinach dumplings from the water and serve with any sauce.