2 tablespoons vegetable oil
1 5-to-6-pound first-cut or flat-cut brisket, cut into 3 pieces
Kosher salt and freshly ground pepper
4 cloves garlic, smashed and peeled
1 12-ounce bottle stout beer
4 stalks celery, cut into large pieces
2/3 cup packed dark brown sugar
1/2 cup tomato paste
1/2 cup red wine vinegar
1/3 cup dijon mustard
1/3 cup soy sauce
2 bay leaves
1 teaspoon paprika
2 brioche or other rolls, split open and toasted
Coleslaw, for serving