1. Preheat the oven to 350°F. Grease and flour two 9-inch cake pans.

2. Toast the coconut: Spread the coconut evenly on a large baking sheet. Toast for about 10 to 12 minutes, tossing the coconut occasionally to brown it evenly, until golden brown. Let cool.

3. To make the cake: Sift together the flour, baking powder, and salt into a bowl.

4. In the bowl of an electric mixer fitted with the paddle attachment, or in a large bowl using a hand-held mixer, beat the butter and sugar for about 2 minutes, until light and fluffy. Add the eggs one at a time, beating until completely blended after each addition and scraping down the sides of the bowl. Add half of the flour mixture and then half of the cream of coconut and sour cream, beating until blended. Add the remaining flour, cream of coconut, and sour cream and beat until smooth.

5. Divide the batter between the cake pans and smooth the tops with a spatula. Bake for 30 to 35 minutes, or until a skewer inserted in the center comes out clean and the cake just begins to pull away from the sides of the pans. Let cool, then invert onto a cake rack and turn right-side up.

6. To make the frosting: In the bowl of an electric mixer fitted with the whip attachment, or in a large bowl using a hand-held mixer, whip the cream with the sugar until firm peaks form. In another large bowl whip the mascarpone with the cream of coconut until well blended. Add the whipped cream to the cheese mixture and blend together until well combined and light and fluffy.

7. To frost the cake: Place one layer on a cake plate, with 3 or 4 strips of wax paper underneath the cake to keep the plate clean. Brush with ¼ cup of the cream of coconut, and spread a layer of frosting over the top. Sprinkle a little toasted coconut evenly over the layer. Place the second layer on top. Brush with the remaining ¼ cup cream of coconut. Frost the sides and then the top. With your hands, press some of the remaining toasted coconut onto the sides of the cake, then sprinkle the rest evenly on the top of the cake. Remove the wax paper and refrigerate until 30 minutes before serving.