Prep the pan: Heat the oven to 350°F (175°C).
Grease a 9-inch round cake pan and line the bottom with parchment.
Whisk dry ingredients: In a large bowl, whisk almond flour, cocoa, baking powder, salt, and espresso powder (if using) until no lumps remain.
Combine wet ingredients: In a second bowl, whisk eggs, granulated sugar, and brown sugar until slightly thick and lighter in color, about 1 minute. Add melted butter, melted chocolate, milk, and vanilla. Whisk until smooth.
Bring it together: Pour wet ingredients into the dry.
Stir with a spatula until just combined. The batter will be thick and glossy.
Bake: Spread batter into the pan and smooth the top. Bake 22–28 minutes, until the center is set and a toothpick comes out with a few moist crumbs.
Cool: Let the cake cool in the pan for 10 minutes, then turn out onto a rack.
Peel off parchment and cool completely.
Finish and serve: Dust with cocoa or powdered sugar. Slice and serve with berries and whipped cream.