Place first 5 ingredients in a 5-qt. slow cooker; toss to combine. Top with bratwurst. Mix broth and seasonings; pour over top., Cook, covered, on low 6-7 hours, until sausage is cooked through and vegetables are tender. Remove sausages from slow cooker; cut into 1-in. slices. Return sausages to potato mixture; stir in cream., Mix cornstarch and water until smooth; stir into stew. Cook, covered, on high until thickened, about 30 minutes.