• Preheat the oven to 350º Fahrenheit and generously grease an 8-inch round cake pan and line it with parchment paper. Or you can grease two 6-inch round cake pan and line it with parchment paper.
• In a bowl, combine the almond flour, cocoa powder, espresso powder, if using, and the baking powder. Mix well and then set aside.
• Place the unsweetened chocolate pieces in a microwave safe bowl and microwave in bursts of 20 seconds, until completely melted.
• In a large bowl combine the butter and sweetener. Cream it together with an electric beater until light and fluffy.
• Add the eggs, one at a time, and beat for 2 to 3 minutes.
• Mix in the melted chocolate, sour cream and the vanilla extract.
• Now add the almond flour-cocoa powder mixture and mix in with a rubber spatula. Once all the flour is incorporated, beat on high for a minute.
• Pour the batter into the prepared pan.
• Bake for 25 minutes.
• Place the cake pan on a wire rack and let the cake cool in the pan for 20 minutes. Take it out of the pan and let it cool completely before frosting.

Make the Whipped Cream Frosting:

• While the cake cools, place a glass or metal bowl with the paddles of the electric beater in the freezer to chill for at least 10 minutes.
• Add heavy whipping cream to the chilled bowl and whip for 2 to 3 minutes, on high speed, till soft peaks appear.
• Add the powdered sweetener and vanilla extract and whip until the peaks are stiff and it holds it shape.
• Spoon lightly onto the cooled cake. Decorate with sprinkles or chocolate shavings if you'd like.
• Store in an airtight container in the refrigerator.