8 tablespoons unsalted butter
½ cup milk
½ cup granulated white sugar
½ cup brown sugar, firmly packed
Pinch of salt
1 teaspoon vanilla extract
½ cup unsweetened cocoa powder
2 cups confectioners’ sugar
Mix butter, milk, salt, brown and white sugars in a heavy pan on medium heat. Bring to a boil and stir continuously for 6 minutes.
Remove from heat and cool briefly, then add vanilla, cocoa powder, and confectioner’s sugar. Beat with an electric mixer until fudge is smooth and thick.
Pour onto a buttered baking pan. When cool enough to touch, use a spatula to help roll mixture into log form, wrap it in plastic wrap and place in freezer for 20 minutes.