Beat together eggs, sugar, vegetable oil and vanilla. Alternate while mixing in milk and flour. Spread on a greased 11x17 inch cookie sheet with sides. Bake at 350ºF for 25 minutes. While cake is still HOT from oven, spread 1 cup peanut butter, evenly over cake. Refrigerate until cool. Melt 12 oz. milk chocolate over low-medium heat. Spread chocolate over peanut butter; refrigerate until chocolate layer is semi firm. With sharp knife cut cake into 24 squares. Place back in refrigerator until completely cooled.