Step 1: Assemble Double Boiler
Add 4 oz. chocolate, 1/3 cup of full-fat half and half, and 2 tablespoons of cubed butter to a heatproof bowl set over a saucepan filled with simmering water.
Step 2: Stir Chocolate
Stir chocolate mixture as it melts. Note that it will be lumpy at first, but will come together once chocolate is fully melted. Stir until smooth.
Step 3: Remove From Heat
Remove from heat and stir in 1 tablespoon of light corn syrup and 1 teaspoon of vanilla extract.
Step 4: Serve Or Store
Use immediately on top of ice cream, cake, brownies, and more! Hot fudge will keep in the refrigerator for several weeks.