Place 12 inch of water in a frying pan and bring to a boil. Add the brats, cover and cook for 4 minutes. Turn the brats over and cook for another 4 minutes. They should puff up significantly.

Remove the brats. Pour the water out of the pan and wipe it clean. Heat the vegetable oil in the pan and put the brats back in, turning them frequently so that they brown on all sides. Remove the brats and let them cool on a cutting board, patting off the excess grease.

Cut each brat into one-inch pieces.

Place the breadcrumbs in a bowl.

Peel the onions and dice into small pieces.

Add the chopped onions to the pan and sauté them in the brat grease until the onions soften and become transparent. Save the pan. You will need it later.

Warm the milk slightly and add it to the breadcrumbs along with the eggs, fried onion, and mustard.

Mix until combined.

Season with salt and freshly ground pepper.

Cover the bowl and let it stand room temperature for 1 hour.

Pinch off a portion of the mustard knödel mixture and form a flat disk in your palm. Place a piece of bratwurst in the center and close the mixture around the bratwurst piece. Repeat.

Place a layer of paper towels beside the stove.

Bring a large pot of salted water to a boil.

Add the knödel.

Lower the heat to a  simmer and let the knödel cook for 20 minutes until they are fluffy.

Remove the knödel from the pot and transfer to the paper towels to drain.

Heat the remaining two tablespoons of butter in a medium-sized skillet.

Carefully add the cooked knödel to the skillet and fry them in the butter, gently turning them to brown on all sides.

Remove from the pan, plate, sprinkle with mustard powder and serve immediately with mustard for dipping.