In a saucepan over low heat, stir the coffee mixture and dissolved cornstarch together until hot, but not boiling. Place 1/4 cup confectioner’s sugar and the yolks in a separate bowl and whisk until sugar is dissolved. Add chocolate liqueur.

Pour egg mixture into coffee mixture slowly, constantly stirring (preferably with a whisk) while you are pouring so that the eggs won’t cook. Make sure all ingredients are combined. Let it sit on the heat for about three more minutes, stirring constantly so that the mixture doesn’t harden. If lumps appear, pour through a strainer or sieve while smoothing out the lumps with the back of a spoon.

Meanwhile, beat the whipped topping with the remaining 1/4 cup confectioner’s sugar until stiff. Gently fold the coffee mixture into the whipped mixture. Refrigerate until ready to serve. Can be made up to 36 hours ahead.