Cut pie into cubes. Set aside.
Microwave 1/2 cup butter and chocolate chunks in a glass bowl at HIGH 1 minute. Stir and microwave 1 more minute. Stir until mixture is smooth.
Beat chocolate mixture, sugar, eggs, milk, and half of pie cubes at low speed with a heavy-duty stand mixer until blended.
Add flour and baking powder, stirring with a wooden spoon until blended. Stir remaining half of pie cubes into batter. (Batter will be thick.) Spoon batter into a 13- x 9-inch pan coated with cooking spray.
Bake at 350º for 50 minutes. Cool brownies completely on a wire rack. Cut into triangles or squares.
Note: For testing purposes only, we used Mrs. Edward's Frozen Pecan Pie.