6 tablespoons unsalted butter, softened, cut up
4 oz. unsweetened chocolate, chopped
3 eggs, room temperature
1 1/3 cups sugar
1 teaspoon vanilla extract
3/4 cup all-purpose flour
1/4 teaspoon salt
1. Heat oven to 350°F. Line 9-inch square baking pan with foil; spray bottom of foil with cooking spray. Combine peanut butter and powdered sugar in small bowl until paste forms; roll into 16 balls (about 1 teaspoon each).
2. Microwave butter and chocolate in small microwave-safe bowl on medium 1 minute 30 seconds; stir. Continue microwaving in 15-second increments until completely melted and smooth. Cool to room temperature.
3. Beat eggs in medium bowl at low speed 15 seconds or until blended. Beat in sugar in steady stream until combined; continue beating 30 seconds. Stir in chocolate mixture and vanilla. Whisk flour and salt; stir into chocolate mixture until blended. Stir an additional 30 seconds to develop structure. Spread in pan, tapping on counter to smooth top.
4. Place peanut butter balls on top of chocolate mixture, pressing just slightly into batter and arranging so that each bar will have 1 ball in center.
5. Bake 25 to 30 minutes or until toothpick inserted 1 inch from side comes out clean and when inserted in center comes out with a trace of chocolate. Cool completely on wire rack. Remove from pan using foil; cut into bars.
PER BAR: 215 calories, 12 g total fat (6 g saturated fat), 4 g protein, 27 g carbohydrate, 50 mg cholesterol, 75 mg sodium, 1.5 g fiber