01 - Preheat grill to medium heat, approximately 350°F to 400°F.
02 - Heat butter or olive oil in a skillet over medium heat. Add sliced onions and cook for 3 minutes until translucent and fragrant.
03 - Stir in drained sauerkraut, caraway seeds, black pepper, and sugar. Cook for 5 to 7 minutes, stirring occasionally, until warmed through and flavors have melded. Reduce heat to low and keep warm.
04 - Place halal bratwurst on the preheated grill. Cook for 10 to 12 minutes, turning occasionally, until evenly browned with a crisp exterior and heated through to an internal temperature of 160°F.
05 - Place buns cut-side down on the grill for 1 to 2 minutes until lightly toasted and golden.
06 - Place a grilled bratwurst in each toasted bun. Top generously with warm sauerkraut mixture. Drizzle with mustard and garnish with fresh parsley, jalapeños, or pickles as desired. Serve immediately.