Cook 2 cups granulated sugar and 1 cup milk in a large saucepan to soft-ball stage--235-240˚F. Move off the heat.
Working quickly, add 1 1/2 cups creamy or crunchy peanut butter, 2 cups marshmallow creme or fluff, and 1 teaspoon vanilla extract to the sugar mixture in the large saucepan. Mix well.
Pour into a buttered 8x8 square baking dish and let cool.