For the Weißwurst:

1. In a large pot, bring the water to a boil. Add the onion, peppercorns, and bouquet garni.
2. Reduce heat until the water is just below boiling. Add the sausages and let them poach gently for about 20 minutes. They should not boil, or they might burst.
3. After 20 minutes, turn off the heat and let them sit for another 10 minutes.

For the Brezn (if making at home):

1. Preheat your oven to 425°F (220°C).
2. In a pot, bring the water to a boil and add the baking soda carefully (it can foam up).
3. Drop each pretzel into the boiling water for 20 seconds, then remove and place on a baking sheet.
4. Sprinkle with coarse salt and make a deep cut in the shape of a “U” on the top of each pretzel.
5. Bake in the preheated oven for 15-20 minutes or until golden brown.

Serving:

1. Serve the sausages hot with a side of sweet mustard and pretzels.