CAKE
Step 1
Preheat oven to 325F and grease a 9x13 inch pan very well.
Step 2
In a large bowl, whisk together the almond flour, coconut flour, protein powder, baking powder, and salt.
Step 3
In another large bowl, beat butter with sweetener until well combined. Beat in eggs and vanilla extract, then beat in half of the almond flour mixture. Beat in almond milk and remaining almond flour mixture until well combined.
Step 4
Spread batter in prepared baking pan and bake 35 to 40 minutes, or until center of cake feels set to the touch and is light golden brown. Let cool 20 minutes, and then flip out onto a cookie sheet or other flat surface.
Step 5
When cake is completely cool, stir coffee and rum together and pour evenly over cake. Let coffee mixture soak in.
FROSTING
Step 1
In a large bowl, beat mascarpone and cream cheese together until smooth. Beat in sweetener and vanilla extract. In a medium bowl, beat whipping cream until it holds stiff peaks.
Step 2
Fold whipped cream into mascarpone mixture until well combined.
ASEEMBLY
Step 1
Cut cake crosswise into 3 even rectangles. Using two large lifters, gently lift one rectangle onto a serving plate (the cake is very fragile after being soaked with coffee so it really needs good lifting spatulas underneath it to support it).
Step 2
Spread with about 3/4 cup of frosting, spreading all the way to the edges. Carefully lift another rectangle of cake onto this and spread with ¾ cup frosting. Top with final layer and spread remaining frosting all over top and sides of cake.
GARNISH
Step 1
Using a fine mesh sieve, dust the top of the cake with cocoa powder. Then use a cheese grater to grate dark chocolate over top.
Step 2
Refrigerate cake for an hour or two to set.
