Line an 8x8 or 9x9 inch baking dish with foil, leaving an overhang on the sides. Lightly grease the foil with butter or cooking spray and set aside.

Combine the sweetened condensed milk and chocolate chips in a large microwave-safe bowl. Microwave on high for 1 minute. Stir well. Continue microwaving in 30-second intervals, stirring after each, until the mixture is completely smooth and the chips are fully melted — usually 2 to 3 minutes total.

Stir in the vanilla extract and a pinch of salt. Mix until fully incorporated and the fudge is glossy and smooth.

Pour the fudge into the prepared pan and spread evenly with a spatula. Tap the pan gently on the counter to release any air bubbles and level the surface.

Refrigerate for at least 2 hours, or until firmly set. Lift the fudge out using the foil overhang, peel away the foil, and cut into squares. Store in an airtight container.