Mix the sugar, butter and evaporated milk in a large saucepan. Heat over medium heat until a rolling boil. Boil for about 3 minutes, until 234º F. Make sure to calibrate your thermometer and adjust accordingly. Also, you can test in a bowl of cold water, and it should come together in a soft ball.
2/3 cup evaporated milk, 3/4 cup butter, 3 cups granulated sugar
Remove from the heat. Add the chocolate chips and marshmallow cream, mix until well combined. Stir in the vanilla. Fold in 1 cup M&M's
7 oz marshmallow fluff, 12 oz white chocolate chips, 1 teaspoon vanilla extract, 1 1/2 cup M&M's
Pour into prepared pan. Sprinkle remaining 1/2 cup M&M's over the top. Gently press into the fudge.
Let set until it hardens, approximately 90 minutes.