Line an 8x8 square baking pan with foil (bring foil up over the sides of the pan for easy removal) and spray lightly with nonstick cooking spray. Set aside.

Add chocolate chips, sweetened condensed milk and unsalted butter in a saucepan.

Heat the fudge mixture over medium-low heat, stirring constantly with a spatula until butter and chocolate are melted, and the mixture is smooth. This typically takes about 7-8 minutes on a gas stove, and the fudge should be smooth, even, and much like frosting.

If you underheat, the chocolate could be soupy, and if you overheat, it could seize up and harden in the pan. This is a slow and steady process while stirring.

After the fudge is smooth and melted, pour fudge into the prepared pan and spread evenly with the back of a spoon.

Refrigerate the fudge pan overnight or until completely firm.

Once firm, carefully lift the foil from the pan and set it on a cooking board. Peel foil from the sides of the fudge.

Use a large, sharp knife to cut into squares, wiping chocolate from the knife blade (carefully) between cuts for a smooth cut.

Makes 42 squares