Line a square baking pan (8×8 inches) with parchment paper, leaving an overhang on two opposite sides. This overhang will make it easier to lift the fudge out of the pan later.

Combine the sweetened condensed milk, semi-sweet chocolate chips, and unsalted butter in a medium saucepan over low heat.

Stir the mixture continuously using a silicone spatula or wooden spoon. Make sure to scrape the sides and bottom of the pan to prevent the mixture from sticking or burning.

Keep stirring until the chocolate chips and butter are completely melted and the mixture becomes smooth and glossy. This should take about 5-7 minutes.

Once the mixture is smooth, remove the saucepan from the heat.

Stir in the vanilla extract and a pinch of salt. These ingredients will enhance the flavor of the fudge.

If desired, fold in the chopped nuts. The nuts will add a delightful crunch and nutty flavor to the fudge.

Pour the fudge mixture into the prepared baking pan, spreading it evenly with a spatula. Gently tap the pan on the counter to remove any air bubbles and ensure a smooth surface.

Allow the fudge to cool at room temperature until it is no longer warm to the touch. Then, cover the pan with plastic wrap and refrigerate for at least 2 hours or until the fudge is firm and set.

Once the fudge is fully set, lift the parchment paper overhangs from the pan.

Place the fudge on a cutting board and use a sharp knife to cut it into squares or rectangles of your desired size.