Mix hamburger, sausage, salt, pepper, onion (and garlic if you choose) together in a large bowl. Set aside.
Mix the 3 eggs, evaporated milk, flour and salt together with a wooden spoon. Then with your hands, continue to mix and add flour as needed (but not too much flour). Pinch off into 3 balls.
Roll each ball out onto a floured board, not too thin. Cut into small squares or triangles.
Place a large spoonful of meat in the center of each piece of dough, fold and seal edges (like a ravioli).
Place each Fleischkuekle onto a platter with either wax paper or parchment paper, not letting the pieces touch each other.
Bring a large pot of water to boil, adding 1 tsp. of salt.
Drop each Fleischkuekle into the boiling water; boil for 20 minutes. You may need 2 pots of water depending on whether you double the batch or not.
Prepare bread crumbs in butter, frying until lightly brown.
Drain and layer the Fleischkuekle onto a clean, dry platter; sprinkle w/fried breadcrumbs between each layer.