Whisk the cream and water together in a measuring cup. Pour into a medium saucepan over medium heat. Add the sweetener and butter.
Bring to a simmer, whisking until the sweetener dissolves. Cook 5 minutes, whisking frequently. Do not let it boil.
Remove from heat and add the chopped chocolate and let sit 3 minutes, to melt. Add the vanilla extract, espresso powder, and salt and whisk until smooth.
Drizzle over your favorite low carb ice cream or use as chocolate fondue. It can also be used to glaze cakes or donuts.
