Preheat oven to 400 degrees and place in it a Pyrex oblong dish with enough butter in it to melt and cover the bottom 1/4 inch thick. Place flour in bowl and combine with the rest of the ingredients and mix well. Let stand for 1 hour. Pour batter into Pyrex and bake at 400 for 20 minutes. Reduce heat to 350 and bake for 10-15 minutes longer. Cut into squares and serve with prime rib and au jus.