Miss Irene Thompson’s Dark Chocolate Frosting

In the top of a double boiler set over hot, not simmering, water, heat the chocolates and butter. (Don’t let the bottom of the container touch the water.) Stir often with a silicone spatula until almost completely melted.

Remove the chocolate mixture from the heat and, with the silicone spatula, stir until completely melted. Stir in the syrup until fully incorporated. Stir in the vanill