Chocolate-Peanut Butter Phyllo Purses

Preheat oven to 375 °F. Butter 13x9x2-inch baking pan. Line bottom of pan with parchment paper. Melt chocolate and butter in heavy medium saucepan over low heat, stirring occasionally. Remove from heat. Using electric mixer, beat egg yolks and 1/4 cup sugar in large bowl until thick and pale. Stir chocolate mixture into yolk mixture. Using clean dry beaters, beat egg whites in another large bowl until soft peaks form. Gradually add remaining 1/2 cup sugar and beat until stiff but not dry. Carefully fold egg whites into chocolate mixture. Transfer batter to prepared pan. Bake until toothpick inserted into center comes out clean, about 15 minutes. Press down edges until even with middle of brownies. Cool completely. Using 2 1/4-inch-diameter cookie cutter, cut out 12 rounds. (Can be prepared 1 day ahead. Store in single layer in airtight container at room temperature.)