Preheat oven to 350 degrees F.
Line a 9 inch spring form pan with parchment and spray it with olive oil cooking spray.
Place a heat proof bowl over a pot of simmering water.
Melt the butter and chocolate together. Stir well. Remove from heat and set aside.
Place the egg whites and vanilla stevia into a stand mixer and blend on high until stiff peaks form. Set aside.
In a separate bowl place the egg yolks and Swerve and mix well. Set aside.
In another bowl whisk the cocoa, salt, xanthan gum and espresso powder together.
Stir this into the chocolate mixture.
Add the coffee extract and chocolate stevia to the chocolate mixture and stir until combined.
Finally add the egg yolks to the cooled chocolate mixture in the stand mixer and blend until combined.
Fold the egg whites by hand into the chooclate mixture in small portions until incorporated.
Pour batter into the pan and bake 40-45 minutes or until a toothpick in center comes out clean.
Allow to cool at least one hour before removing.
Once cool you can frost and a refrigerate cake until ready to serve.
Make frosting by adding all ingredients to a stand mixer and blend on high until thickened.
Spread over cake and sprinkle with chocolate shavings if desired.