Place Bratwurst in saucepan and cover with boiling water. Cook 3 mins; drain. Melt butter in a skillet; add Bratwurst to brown.
Remove to a warm plate. Pour off all except 2 Tbs fat. Add onions; saute until tender. Return sausages to skillet. Add bay leaves, beer, salt and pepper. Cook slowly for 15 mins. Add more beer during cooking, if nedded.
Remove Bratwurst to a warm platter. Mix flour with a little cold water; stir into hot liquid. Cook, stirring, until liquid is a thick sauce; remove bay leaves. Add parsley; pour over sausage. Serve with mashed potatoes and red cabbage. Serves 4.
Notes: The small whitish sausages called Bratwurst originated in Nurnberg, but are used in Berlin in this specialty.