Cut a sheet of waxed paper 10-12 inches square. Place inside an 8 or 9-inch square baking pan, creasing the paper at the corners so that it stays in place.
Pour condensed milk into a saucepan. Add marshmallows. Scrape sides with rubber spatula so that it doesn't stick, as you heat on very low heat. Remove from heat as soon as marshmallows are melted and add baking chocolate. Stir to help chocolate melt evenly. Add kisses and stir until melted. Put on low heat if not melting, but only for a few seconds so that it doesn't burn. When mixture is very smooth, stir in vanilla and nuts.
Spread fudge into prepared pan and smooth the top so that it is not too uneven. Refrigerate at least 2 hours. Cut into squares. Store in covered container in refrigerator.
