Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper for easy removal.

In a blender or food processor, combine the cold cooked quinoa, melted butter, eggs, milk, and vanilla extract. Blend until the mixture is completely smooth and creamy, with no visible quinoa pieces.

In a large mixing bowl, whisk together the sugar, cocoa powder, baking powder, baking soda, and salt.

Pour the blended quinoa mixture into the dry ingredients. Stir gently with a spatula or wooden spoon until everything is well combined and no dry streaks remain. The batter should be thick and smooth.

Pour the batter into your prepared cake pan. Smooth the top with a spatula. Bake for 40–45 minutes, or until a toothpick inserted in the center comes out mostly clean with a few moist crumbs. Let the cake cool in the pan for 10–15 minutes, then transfer to a wire rack to cool completely before frosting.

In a small saucepan over low heat, warm the heavy cream just until it begins to steam do not boil. Remove from heat and stir in the chopped dark chocolate. Let it sit for 1–2 minutes to melt, then stir until smooth. Whisk in the confectioners’ sugar until fully combined and glossy.

Once the cake is fully cooled, spread the frosting evenly over the top with an offset spatula or back of a spoon. Allow frosting to set for 10–15 minutes. Slice and serve!