Prepare a microwave-safe dish. You can use a glass or ceramic dish that's suitable for microwave use.
In a microwave-safe bowl, combine the semi-sweet chocolate chips and unsalted butter.
Microwave the mixture in 20-30 second intervals, stirring each time, until the chocolate and butter are completely melted and well combined. This should take about 1-2 minutes, but be careful not to overheat it.
Once the chocolate and butter are smooth, stir in the sweetened condensed milk, vanilla extract, and a pinch of salt. Mix until everything is well combined.
Microwave the mixture for an additional 1-2 minutes, stopping to stir every 30 seconds. The fudge should become thick and glossy.
Pour the fudge mixture into the prepared dish, spreading it out evenly.
If you'd like, you can sprinkle chopped nuts, sea salt flakes, or sprinkles on top of the fudge for added flavor and decoration.
Let the fudge cool at room temperature for about 2 hours or until it's firm.
Once the fudge has set, cut it into small squares or rectangles.
Store the microwave fudge in an airtight container at room temperature or in the refrigerator for longer shelf life.Enjoy your delicious homemade microwave fudge!