Making fudge with Marshmallow Fluff makes it easier to get fudge that turns out perfectly smooth and creamy, but it's important to follow the directions. Stir the granulated sugar into the Fluff, milk, and other ingredients until it's dissolved. Cook the mixture for the exact times listed in the recipe. Trying to rush or shortcut these steps will result in fudge with an off texture or that doesn't set properly.