Step 1: Preheat the oven to 325 F and grease 2 mini-loaf pans. Line bottom and long sides of pans with parchment paper, and grease paper.
Step 2: In a medium, microwave-safe dish, melt butter. Stir in cocoa powder until smooth. Set aside.
Step 3: In a medium bowl, whisk together almond flour, erythritol, baking powder, baking soda, xanthan gum and salt.
Step 4: In a larger bowl, beat eggs with electric mixer until frothy. Beat in ricotta, almond extract and stevia until smooth. Add dry ingredients and beat until thoroughly combined.
Step 5: Place half of batter into chocolate mixture and mix until thoroughly combined. Alternating between light and dark mixtures, spoon dabs of batter into prepared pans until they are 2/3 full.
Step 6: Place pans on a baking sheet and bake for 30-35 minutes or until top is set and a tester inserted in the middle comes out clean.