Rose Rubin'S Cookies
["1/2 lb. soft butter (must use butter)", "7/8 c. sugar", "4 egg yolks", "1 tsp. vanilla", "2 1/2 c. all-purpose flour"]
["Cream butter and sugar.", "Add egg yolks, each one separately. Add vanilla and flour.", "Make into dough ball.", "Wrap in wax paper. Refrigerate at least 2 hours or overnight.", "Form little marble shaped balls.", "Press thumb in center.", "Put jelly in center part (strawberry, black raspberry, apricot or desired flavor).", "Bake 12 to 15 minutes in 400\u00b0 oven."]
["butter", "sugar", "egg yolks", "vanilla", "flour"]