1.   Place the rack in the middle position of the pre-heated oven set to 350 F or about 177 C. Line the bottom of an 8 inch or 20 cm square baking ban. Use the butter to grease the top of the parchment and sides of the pan. Set aside

2.   Prepare a bain Marie / double boiler set over medium heat. To the bowl add the butter, the chopped chocolate, cocoa powder and espresso powder. Place the bowl over the pot with simmering water. Stir as the chocolate and butter melt until the mixture is velvety smooth. Let cool to room temperature

3.   To a large bowl, add the eggs and the powdered sweetener. Whisk to a pale yellow and fluffy stage

4.   Place a sieve over the bowl and add the almond flour, lupin flour and salt, then whisk to sift. Stir until well incorporated

5.   To the chocolate mixture add either the rum or rum extract, and also add the heavy cream to thin out the ganache. Stir well to combine

6.   Pour the cooled chocolate mixture into the bowl with the egg yolks. Whisk until well combined and mixture is homogeneous. Sprinkle the baking powder over the batter and whisk to incorporate very well

7.   Pour batter into the lined cake pan. Place into the preheated oven and bake for 25 – 30 minutes. Test with a toothpick to make sure cake is done. Remove cake from oven, let cool for 5 minutes, then remove cake from pan. Peel off the bottom parchment paper and transfer to a cooling rack. When cooled, cut into 3 rows by 3 rows (9 squares) or 4 rows by 3 rows (12 squares) or 4 rows by 4 rows (16 squares). Dust with either a tbsp of cocoa or combine cocoa and 1 tsp of additional powdered sweetener. Serve and enjoy!