In a large sauce pot melt the butter. Add the onions and the garlic. Sweat the onions and garlic for 3 - 5 minutes. Add the bratwurst, and all of the beer. Bring the beer mixture to a boil, reduce and simmer for 15 minutes. Turn off the heat and let the brats cool in the beer mixture. Heat butter in a saute pan over low heat. Roll the brats in seasoned flour and brown the sausages on all sides. Serve with sauerkraut.