2 French baguettes, heated
3 12 ounce cans light beer
2 tablespoons tablespoons butter
4 medium onions, sliced
1 cup dark beer
1 tablespoon dark brown sugar
1/4 cup whole grain mustard
1 tablespoon Dijon mustard
1/8 teaspoon cayenne pepper
In a medium bowl, place brats evenly in the bottom of the bowl and pour light beer over. Cover and refrigerate overnight.
To make relish, saute onions in butter in a large skillet over medium heat until caramelized, about 15 minutes.
Stir in the dark beer, brown sugar, mustards and cayenne.
On a hot grill, grill the marinated brats until well marked and cooked through, or until plumped and no longer pink. Keep them in the hot relish mixture in the oven until they are all grilled and you are ready to serve.
Slice the hot baguettes in half, not cutting all the way through so that the halves stay connected. Slice baguettes into 6 inch pieces, fill with brats, and slice these in half. Pile each one generously with hot onion relish. Serve immediately.