Preparation / Directions:
Make the peanut butter bars: Position a rack in the center of the oven and preheat to 350øF. Butter a 13-by-9-inch baking pan. In a medium bowl using a wire whisk, stir together the flour, baking powder and salt. In a large bowl, using a hand held mixer set a medium speed, beat the butter and both sugars for 2 to 3 minutes, until the mixture is light in color and texture. Scrape down the side of the bowl with a rubber spatula. Beat in the peanut butter. Beat in the eggs one at a time, beating well after each addition. At low speed, beat in the flour mixture in two additions, scaping down the side of the bowl after each addition. (The batter will be stiff.) Scrape the batter into the prepared pan and smooth the top with the rubber spatula. Bake for 20 to 25 minutes, or until a toothpick inserted in the center comes out clean but not dry.
Make the topping: Remove the baking pan from the oven and scatter the chocolate chips evenly over the top of the peanut butter bars. Return the pan to the oven for 2 to 3 minutes to melt the chocolate. Using a rubber spatula, spread the melted chocolate chips evenly over the tops of the bars. Scatter the peanuts evenly over the chocolate. Cool the bars completely in the pan set on a wire rack. Using a large, sharp knife, cut the peanut butter bars lengthwise into 4 strips. Then cut each strip into 6 pieces, to make 24 squares. The bars can be stored, layered between sheets of waxed paper, in an airtight container at room tempature for up to 3 days.