Heat oven to 375°F and line a baking sheet with parchment. on medium heat, melt 5 ounces chocolate in a glass bowl, for 30 intervals, stirring each time until smooth.
Add butter and for ten seconds microwave the bowl. Stir. Repeat until smooth. Set aside while you prepare the batter to allow to slightly cool.
Beat three eggs in a large bowl, and ½ cup granulated sweetener on high until the eggs become pale and mixture becomes frothy. This should take about 3-5 minutes.
Add the mascarpone cheese and until smooth beat it.
Sift in ½ tsp salt and half of the cocoa powder (2 tablespoons) and gently mix. You need to go slow as the power will resist mixing with the egg.
Sift in another 2 tablespoons of the cocoa powder and stir until the batter forms and all of the mixtures is dissolved properly.
Make sure your chocolate is still melted. Heat for 10 seconds and stir If not. Into the batter fold the melted chocolate and mix well until there are no lumps and it is creamy.
Pour batter into prepared 8x8 pan and for 25 minutes or until the center no longer jiggles bake at 375°F.
Remove from pan and before cutting cool it completely.