Melt the chocolate and cream in the top of a double boiler over hot water (or set a heat-safe bowl over a pot of simmering water). Cook and stir until smooth, with heat on low, stirring occasionally.
Combine the sugar, flour and salt; add enough of the chocolate mixture to make a smooth paste. Blend into the remaining chocolate mixture. Cook until smooth and slightly thickened, about 10 minutes.
Remove from heat and stir in the remaining ingredients.
Notes
If you are preparing this recipe as gluten-free, just be sure to use brands of chocolate and vanilla that are known to be GF.
This sauce should be refrigerated. It reheats easily