Cut your bread rolls into 1/2 - 3/4 inch (1-2 cm) pieces. Do not remove the crust. Add to a large bowl/pot.
6 bread rolls, soft pretzels, or bread
Heat the milk until very warm but not boiling and pour over the bread rolls. Press with the back of a spoon and let soak for 10-15 minutes or until softened (it may take longer if your bread is really dry).
1 cup milk
In the meantime, dice the onions. Heat butter in a medium pan. When hot and bubbling, add the onions. Cook for about 8-10 minutes until soft and golden.
1 large onion, 2 tablespoons butter
Add the onions to the soaked bread rolls. Then add chopped parsley, beaten eggs, cooked and crumbled bacon (if using), nutmeg, salt, black pepper, and 2 tablespoons of fine breadcrumbs.
3 tablespoons chopped parsley, 3 large eggs, 1/4 cup crumbled cooked bacon, 1/4 teaspoon nutmeg, 1 tablespoon salt, 1/4 teaspoon black pepper, 2-4 tablespoons fine breadcrumbs
Knead with your hands until all the ingredients are well combined. The mixture should be slightly sticky. Use more breadcrumbs if the mixture is too loose and more milk if it's too dry (after you make a couple of batches, you will be able to assess it easily; it's difficult to write the exact measurements for the milk in this recipe because it will depend on how much of bread rolls do you have and how dry they are).
Form 12 round balls from the mixture and place on a wooden board. They will be about the size of a tennis ball. If the mixture is too sticky, wet your hands with water. Press the balls well so they are nice and compact.
Heat a large pot filled with salted water. Reduce the heat to the lowest and add 4 balls to the water. The water should barely simmer, it can't boil rapidly or your Knödel will fall apart! It would be best to test-cook just 1 Knödel first to check if it's not falling apart. Let the balls cook in the water for 20 minutes, take out of the water, and repeat with the remaining balls.
The Semmelknödel are ready to eat as they are or you could cut them into thick slices and pan-fry in butter until crispy and golden, sprinkle with salt (this is my favorite way to eat them).
Enjoy!