Place four cups of mini marshmallows into the freezer until frozen.

In a large bowl, place broken milk chocolate bars, chocolate chips and butter pieces; set aside. In a large pan, combine sugar, evaporated milk and 2 1/2 cups mini marshmallows. Bring to a boil over medium heat while stirring constantly, then, continue to cook and stir at a light boil for 7 minutes.

Remove from heat and immediately pour over the chocolate/butter mixture. With a wooden spoon, stir the mixture until the chocolate is melted and loses its shine. Don't worry if it looks separated, just keep stirring. As it starts to cool it will lose its shine. Stir in the vanilla. Add the frozen marshmallows and walnuts/pecans. Spread into a large buttered cookie sheet (for a full batch I used two 9x13 baking dishes).

Cool completely. You can speed this up by putting it in the refrigerator. Cut into pieces and serve. Store in an airtight plastic container. Makes about 60-70 pieces.