Break up the chocolate and place in a bowl together with the butter. Cook at 50% power in the microwave until almost melted, then stir until fully melted.
Beat three eggs together in a stand mixer bowl, then add heavy cream, sweetener, unsweetened cocoa powder, and vanilla extract. Beat until fully combined, then add the chocolate and butter mixture and beat again until smooth.
Pour the mixture into a greased 9" pie pan, and bake until the center is firm but slightly wobbly, about 15-18 minutes.
Let the torte cool completely, then cover and place in the fridge until required.
Serve with whipped cream and/or a sprinkle of confectioner's Swerve.
4g net carbs per serving (one eighth of the torte)