Line an 8x8 inch baking pan with parchment paper, leaving some overhang to help lift the fudge later. Set aside.

In a microwave-safe bowl, combine the milk chocolate chips and sweetened condensed milk. Do not stir. Add the cubed butter on top. Microwave on high for 2 minutes. The butter may not be completely melted at this point.

Stir the mixture until smooth and all the butter and condensed milk are fully incorporated into the chocolate.

Add the cinnamon whisky and vanilla extract, stirring until the fudge mixture has a uniform consistency.

Pour the fudge mixture into the prepared baking pan and spread into an even layer. Tap the pan gently on the counter to release any air bubbles.

Chill in the refrigerator for at least 2 hours, or until the fudge is completely set.

Using the parchment paper overhang, carefully lift the fudge from the pan. Slice into equal-sized pieces with a sharp knife.