Mix four with cold milk first. In a large pot over medium heat, add can of condensed milk, milk, vanilla, flour and egg yolks. (save egg whites for topping) Sitrring often, cook until sauce had begun to thicken. Remove from heat. In a large bowl, place vanilla wafers on the bottom. Then layer with bananas. Add sauce. Continue until sauce is used up. Beat egg whites with 1/4 cup sugar until stiff peak is formed. Put over banana pudding. Bake at 350 degrees until top is golden brown.