Preheat your oven to 350°F and lightly grease a 9-inch square baking pan with a small amount of coconut oil.
In a large mixing bowl, whisk together the oat flour, cocoa powder, chocolate protein powder, baking powder, and sea salt until no lumps remain.
In a separate medium bowl, combine the Greek yogurt, eggs, egg whites, melted coconut oil, maple syrup, and vanilla extract, whisking until the mixture is smooth.
Fold the grated carrots into the wet ingredients, then gradually stir the dry flour mixture into the wet base until just combined.
Pour the batter into the prepared baking pan and bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool slightly, then whisk the coconut milk until creamy and drizzle it over the top before slicing into four equal portions.