Preheat oven to 350°. In large bowl, stir espresso powder and 1 tablespoon water until coffee dissolves. Add flour, sugar, butter, baking powder, almond extract, and egg; with mixer at low speed, beat ingredients until blended, occasionally scraping bowl with rubber spatula. Stir in walnuts. Spread dough in ungreased 9 x 9 inch baking dish. Bake 20 to 25 minutes, until toothpick inserted comes out clean. Remove pan from oven to wire rack. Immediately sprinkle chocolate pieces over hot cookie; let stand 5 minutes. Evenly spread melted chocolate over top of cookie. Cool in pan on wire rack until chocolate is firm. When cold, cut into 3 strips, then cut each strip crosswise into 9 bars. (abt 110 calories each)