The filling of a German Chocolate Cake is a delectable mix of evaporated milk, sugar, egg yolks, butter, vanilla extract, chopped pecans, and shredded coconut. This mixture is cooked until it thickens and takes on a creamy, gooey texture, perfectly complementing the chocolate layers of the cake. The combination of coconut and pecans provides a delightful contrast in textures, adding to the cake's uniqueness.