Combine the heavy cream, decaf coffee, and instant coffee granules in a medium saucepan over medium heat, stirring occasionally, until it comes to a simmer.
In a separate bowl, whisk together the egg yolks and sugar until light and fluffy.
Slowly pour the hot coffee mixture into the egg mixture while whisking continuously.
Return the mixture to the saucepan and cook over medium heat until it thickens into a custard.
Remove from heat and stir in the vanilla extract.
Strain the mixture through a fine mesh sieve to remove any lumps or bits of egg.
Let the ice cream mixture cool completely, then chill it in the fridge for at least 2 hours or overnight.
Once chilled, pour the mixture into your ice cream machine and churn according to the manufacturer's instructions.
When it's done, transfer the ice cream to a container, cover with plastic wrap, and freeze for at least 4 hours or until firm.
Serve with a dollop of whipped cream and some chocolate chips or coffee beans for an extra special touch.