Heat Dairy: In a medium saucepan, combine the cream, milk, sugar, cocoa powder, corn syrup, and salt. Heat over medium, stirring occasionally, until steaming but not boiling.

Whisk Yolks: In a separate bowl, beat the egg yolks until smooth.

Melt Chocolate: In another small bowl add the chopped chocolate. Add one big ladleful of hot milk over the chocolate and set aside to melt.

Temper Eggs: Slowly drizzle a ladleful of hot milk mixture into the yolks, whisking constantly. Repeat with several more spoonfuls of hot cream (this process slowly warms the eggs, so they don’t scramble). Then pour the tempered yolk mixture back into the saucepan. Cook for 30 more seconds or so, until 170-175 degrees F (or the mixture thickens just slightly and coats the back of a spoon). Do not let it boil.

Combine: Stir in melted chocolate and vanilla extract. Strain the mixture through a fine-mesh sieve into a clean container.

Chill in refrigerator for at least 4 hours or ideally overnight.

Churn cooled custard in an ice cream maker according to manufacturer’s instructions.

Fudge Swirl and Freeze: Transfer half of the mixture to ice cream container. Spoon 3 tablespoons warmed fudge sauce into a line over the top, then use a knife to gently swirl it into the ice cream. Top with remaining ice cream and add another layer of fudge drizzle on top. Freeze for at least 4 hours, until firm and scoopable.

Serve in a homemade waffle cone, if desired.