Set chocolate chips, Marshmallow Crème, vanilla extract, Bailey's and nuts in a very large bowl. Set aside for later.
Bring butter, sugar and milk to a boil and then cook slowly for exactly 11 minutes, stirring constantly. Pour milk mixture over the other ingredients and stir slowly to blend. Do not use a mixer. Pour into a buttered 13 x 9-inch pan and chill very well. Cut when cold.
