-(salted) Beat butter and sugar together until creamy. Blend in egg and vanilla. Sift together flour, baking powder and salt. Add to creamed mixture; blend well. Stir in oats. Divide dough in half. To one half, add melted chocolate; add peanuts to remaining dough. Roll out chocolate dough between two sheets of waxed paper to form a 15x10-inch rectangle. Roll out peanut dough between two sheets of waxed paper to form a 15x10-inch rectangle. Place peanut dough on top of chocolate dough, removing all waxed paper. Starting with long side, roll up as for jelly roll. Wrap in waxed paper and chill several hours or overnight. Cut into 1/4-inch slices. Place on ungreased cooky sheets. Bake in preheated moderate oven (350 F.) 10 to 12 minutes.