Line an 8x8 inch pan with parchment paper or foil. Spray with baking spray and set aside.
In a heavy-bottomed pan set over low heat, combine the chocolate chips, butterscotch chips, and sweetened condensed milk. Stir until melted and completely smooth and combined.
Remove from heat. Stir in vanilla extract. Pour the chocolate mixture into the prepared pan and spread evenly. Sprinkle flaked sea salt over the top. Let cool completely at room temperature. Remove from pan and cut into 36 1-inch squares. Store in an airtight container.
Notes
Heat the chips and sweetened condensed milk over low heat. Slow and low is the key to this mixture coming out silky smooth.
Add the vanilla extract off the heat, after the chips are melted.
Always prepare the pan with parchment paper or foil sprayed with baking spray to ensure easy removal of fudge.
Top the mixture with salt immediately after spreading in the pan so that the salt sticks.
Let the fudge cool completely at room temperature before slicing. Speed up this process by chilling the fudge in the refrigerator for at least an hour.