Combine chocolate chips, sugar, heavy cream, corn syrup, cocoa powder, and salt in a small saucepan over medium heat.
Cook, stirring frequently, until chocolate is melted and sugar is dissolved.
Bring to a boil over medium heat. Boil, stirring constantly, for 3 minutes. Remove from heat.
Add butter and vanilla extract. Stir well. Mixture will be very thin/liquidy, but will thicken and become fudgy as it cools. Allow mixture to cool to desired consistency before serving over ice cream. If cooled completely, fudge will be too thick to pour and you will want to heat in the microwave for several seconds before serving (it is supposed to be “hot” fudge, after all).
¹You can use natural or Dutch processed cocoa powder, I personally prefer the taste of Dutch processed in this recipeLeftover fudge sauce will keep in an airtight container in the refrigerator for 1-2 weeks.