Combine 1/2 cup butter, 1/4 cup powdered sugar and cocoa in 2-quart saucepan. Cook over medium heat, stirring occasionally, until butter is melted. Remove from heat. Add all remaining base ingredients; mix well. Press mixture onto bottom of ungreased 8-inch square baking pan. Combine all filling ingredients in large bowl. Beat at medium speed, scraping bowl often, until creamy. Spread evenly over crust. Refrigerate at least 30 minutes or until firm. Meanwhile, combine 2 tablespoons butter, 2 tablespoons half and half and corn syrup in 1-quart saucepan. Cook over medium heat, stirring occasionally, 2-3 minutes or until mixture comes to a boil. Remove from heat; stir in chocolate chips until melted. Pour chocolate into medium bowl. Mix in enough powdered sugar for desired spreading consistency. Spread glaze evenly over filling. Cover; refrigerate at least 2 hours or until serving time. Store refrigerated.