1 tablespoon butter, plus more for rolls (optional)
1 small red onion, halved and thinly sliced
1 -- (14-ounce) can sauerkraut, well drained
1 teaspoon sugar
1/2 teaspoon caraway seeds
-- Coarse salt and ground pepper
4 -- precooked bratwurst sausages (3-ounces each)
4 -- hard rolls, halved horizontally
1/4 cup spicy brown mustard
1/2 cup bread-and-butter pickles
-- Potato chips, for serving
Heat grill to medium-low; lightly oil grates.
In a medium saucepan, heat butter over medium. Add onion and cook, stirring occasionally, until soft, 4 to 5 minutes. Add sauerkraut, sugar, caraway seeds and 1/2 cup water; season with salt and pepper. Simmer until sauerkraut is heated through, 3 to 5 minutes; set aside.
Grill sausages, turning frequently, until golden brown and warmed through, 10 to 12 minutes. Grill rolls, cutside down, until warm, 1 to 2 minutes. Spread lightly with butter, if using, and mustard. Halve sausages lengthwise; fill each roll with 2 halves and pickles. Serve with sauerkraut and potato chips.