Heat heavy cream in a heavy pan on medium heat until it comes to a boil.

Remove from heat and stir in chocolate until the mixture is smooth. Stir in optional flavoring.

Let chocolate mixture cool, whisking occasionally.

When cool but not yet set, beat vigorously. Add butter and flavoring and beat until fully incorporated.

Store in fridge in air tight container.

If refrigerated for more than 2 hours, bring to near room temp and whip again if needed.