Heat oven to 350. Microwave 4 squares of chocolate and 1/2 cup butter in large microwavable bowl on High 2 minutes or until butter is melted. Stir until chocolate is completely melted.
Stir sugar into chocolate until well blended. Beat in eggs, 1 at a time, with electric mixer on low until completely mixed. Add vanilla. Stir in 1/3 c flour, baking soda and salt. Beat in remaining flour alternately with water until well blended and smooth. Pour into greased and floured 13 x 9" baking pan.
Bake 30 minutes or until toothpick inserted into center comes out clean. Cool completely in pan on wire rack.
Mix coconut and milk until well blended. Spread on top of cake.
Microwave cream and 2 T butter in large microwavable bowl on High 2 minutes; stir. Microwave 30 seconds or until mixture boils. Add 10 chocolate squares; stir until completely melted. Stir frequently until mixture is cool and of spreading consistency.
Spread over coconut layer. Let stand until chocolate is firm. Cut into bars.