In a microwave-safe bowl, add the chocolate chips, butter, vanilla extract, salt, and sweetened condensed milk. Microwave in 30-second increments, stirring well each time, until the fudge is smooth and glossy (this will take about 6 microwave cycles, give or take).
3 cups chocolate chips, 2 tablespoons salted butter, 1 teaspoon vanilla extract, Pinch of salt, 14 ounces sweetened condensed milk