Melt margarine in a double boiler.
Pour over confectioner sugar, peanut butter, vanilla, and salt in a bowl.
Mix well. Pour into pan.
Melt chocolate chips in a double boiler until there are no lumps and spread over fudge.
Refrigerate until hard (about 45 minutes).
Tip: Do not let the chocolate get too hard or it will crack when you cut it. Score it when halfway hardened.