Prep the pan. Line an 8x8-inch metal pan with parchment, leaving overhang for easy lifting. Lightly grease the parchment. Preheat oven to 350°F (175°C).

Melt fats and chocolate. In a small saucepan or microwave-safe bowl, melt the butter and half of the chopped sugar-free dark chocolate. Stir until smooth. Whisk in the oil and vanilla. Set aside to cool slightly.

Whisk dry ingredients. In a bowl, combine 1 cup fine almond flour, 1/2 cup cocoa powder, 1/2 teaspoon baking powder, 1/2 teaspoon salt, and 1/2 teaspoon espresso powder (optional). Break up any clumps.

Beat eggs with sweeteners. In a mixing bowl, whisk 3 large eggs with 1/2 cup granular sweetener and 1/3 cup powdered sweetener for 1–2 minutes until slightly thick and lighter. This helps create the crackly top.

Combine wet and dry. Slowly stream the warm chocolate-butter mixture into the egg mixture while whisking. Fold in the dry ingredients just until combined. Do not overmix.

Add chocolate chunks. Fold in the remaining chopped chocolate. The batter will be thick and glossy.

Pan and smooth. Spread batter into the prepared pan. Smooth the top with an offset spatula. Sprinkle a pinch of flaky sea salt if you like.

Bake. Bake for 18–24 minutes. Start checking at 18. The edges should be set, and a toothpick inserted 2 inches from the edge should have moist crumbs. The center should look slightly underbaked.

Cool for clean slices. Cool in the pan on a rack for at least 45–60 minutes. For the fudgiest texture and a crisper top, chill for 30 minutes before slicing with a sharp knife.

Serve. Lift out using the parchment. Cut into 16 squares. Enjoy as is, or warm briefly and top with sugar-free whipped cream.