Preheat the oven to 350 degrees. Grease the bottom of a 9-inch springform pan with butter. Cut a piece of parchment or waxed paper in a circle to fit the bottom of the pan. Place the paper in the pan and grease it with butter.

Melt butter and chocolate together in a microwave (2-3 minutes) or on top of a double boiler.

In a separate bowl, mix together 1½ cups Swerve, 1 cup cocoa powder, 1 teaspoon instant espresso or coffee, and salt. Add to the melted chocolate mixture, then add the eggs and 2 teaspoons vanilla and mix well. Pour the batter into the prepared pan.

Bake for 45 minutes. Let cool in the pan until completely cooled. Remove the ring from the pan and transfer the cake to a serving plate or platter.

Combine the heavy cream with 2 tablespoons Swerve, 1 tablespoon cocoa powder, 1 teaspoon instant espresso or coffee, and 1 teaspoon vanilla in an electric mixer. Beat on high until stiff peaks form.

Spread the cream on top of the cake and dust with more cocoa powder, if desired.