For the brownie layer: Preheat oven to 350 degrees. Melt the butter. Add the sugar and eggs and beat together. Add the rest of the ingredients and mix. Pour the batter into a greased 9" spring form pan. Bake for 15 minutes, until toothpick comes out clean.
For the coconut filling: While the brownie layer is cooking, in a medium saucepan, combine the half and half, coconut milk, eggs, sugar, cornstarch and salt and cook over medium/low heat until the mixture thickens, about 8-10 minutes. Once the mixture is thickend, remove from heat and add the vanilla, coconut extracts and the untoasted flaked coconut and stir to combine. Pour this over the brownie layer. Place plastic wrap directly on top the coconut cream to keep a film from forming and chill in the fridge for at least 2-4 hours, or until completely cold.
For the Chocolate Mousse: Melt the butter in a medium bowl set over a sauce pan of simmering water (DO NOT allow the bowl to touch the water) In a separate small bowl, whisk together egg yolks, cream and vanilla and set aside. Once the butter is melted, slowly whisk in the yolk mixture. Continue whisking over the simmering water until the mixture thickens, like pudding, this will take about 8-10 minutes. Once thick remove it from the water and add the chocolates, stirring to melt. Set aside. In a separate bowl beat together the egg whites, sugar and pinch of cornstarch until stiff peaks form. Whisk 1/4 cup of the stiff egg whites into the chocolate to loosen it up. Now add the rest of the egg whites, folding gently until they are completely blended into the chocolate. Pour this mousse over the cold coconut cream in the spring form pan. Place the whole thing back in the fridge and let it set completely, about 4 hours.
Finishing the cake: Make your fresh whipped cream by beating together the whipping cream, powdered sugar and vanilla until peaks form. Add this to the top of the cold cake and then top with toasted coconut.
To serve, run a knife around the edges of the spring form pan to loosen it from the sides. Remove the sides and cut into slices. ENJOY!!