In a large mixing bowl, whisk together the butter and sugars until completely combined and glossy. Whisk in the eggs, one at a time, followed by the vanilla, until combines and smooth. \nIn a separate large mixing bowl, sift together the flour, cornstarch, baking powder, salt and Morocco spice. Using a rubber spatula, stir the dry ingredients into the wet ingredients until completely combined and smooth. Fold in the dark chocolate chunks. \nCoat an 8x8-inch pan with non-stick cooking spray or melted butter. Pour batter into the pan, tapping it a few times on the counter to ensure it’s evenly spread. Let sit at room temperature while your oven preheats to 350 degrees. \nBake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely before slicing and serving.