I made some cocoa fudge a couple weeks ago from a recipe I found on the net (one of the product companies, Nestle, Hershey or Carnation, can't remember which), it directed you to cook the evaporated milk and butter for 4-6 minutes then add the cocoa, marshmallow cream and vanilla, stir to incorporate and spread in pan to cool, I cooked it 6 minutes - it came out like a brick.