1. Preheat oven to 350 degrees. Place the butter and a third of the coconut in the bowl of a food processor fitted with the metal blade. Process until mixture forms a ball, 1 to 2 minutes. Transfer to a medium bowl. Sprinkle remaining coconut over mixture, and combine with your fingers.

2. Place an 8-inch tart pan with a removable bottom on a baking sheet. Press coconut mixture into bottom and up sides of pan to form a crust, leaving top edges loose and fluffy. Place a ring of aluminum foil over edge to prevent burning. Bake until center begins to brown, 10 to 15 minutes; remove foil, and cook until edges are browned, 4 to 6 minutes. Transfer to a wire rack to cool completely.

3. Place chocolate in a medium heatproof bowl. Bring cream just to a boil in a small saucepan, and pour over chocolate. Let sit 10 minutes, and stir until chocolate is melted and combined. Let cool, and pour into coconut crust. Cover with plastic wrap, and transfer to refrigerator until filling is set, at least 1 hour. Cut into wedges, and serve.