In a skillet, melt 1/2 cup butter. Add coconut; cook and stir until golden brown. Remove from the heat. Stir in brown sugar and pecans; mix well. Set aside 1 cup. Press remaining coconut mixture onto the bottom and up the sides of a greased 13-in. x 9-in. x 2-in. dish. In a saucepan over medium heat, melt the chocolate and remaining butter. Add sugar and milk. Bring to a slow boil; cook for 5 minutes. Remove from the heat; stir in vanilla. Cool; pour over coconut mixture. Spread ice cream over top. Sprinkle with the reserved coconut mixture. Freeze for 6-8 hours or overnight. Remove from the freezer 15 minutes before serving. The dessert may be frozen for up to 2 months.