Heat oven to 350°F. Lightly grease 13 x 9 x 2-inch baking pan.
Sift together flour, baking powder and salt onto sheet of waxed paper.
Beat together butter and brown sugar in a large bowl until well blended. Add the eggs, one at a time, beating well after each addition. On low speed, gradually beat in the flour mixture until blended. Beat in the vanilla. Stir in the chocolate and nuts. Spread the mixture evenly into the prepared pan.
Bake in 350°F oven for 30 to 35 minutes or until a wooden pick inserted in center comes out clean.
Whisk together confectioners sugar and enough milk in small bowl until smooth and good drizzling consistency. Cover; set aside.
When cookie is completely cooled, drizzle with glaze. Let stand until glaze hardens. Cut into bars.