PREHEAT oven to 350° F. Generously grease and flour madeleine baking pan(s).
COMBINE flour and 1 cup morsels in medium bowl. Beat eggs, granulated sugar, orange liqueur, vanilla extract and orange peel in large mixer bowl until light in color. Fold flour mixture and butter alternately into egg mixture, beginning and ending with flour mixture. Spoon batter by heaping tablespoon into each prepared mold.
BAKE for 10 to 12 minutes or until wooden pick inserted in center comes out clean. Cool in pan(s) for 1 minute. With tip of knife, release onto wire racks to cool completely. Wash, grease and flour pan(s). Repeat with remaining batter.
SPRINKLE madeleines very lightly with powdered sugar. Microwave remaining morsels in heavy-duty plastic bag on HIGH (100%) for 30 seconds; knead bag to mix. Microwave at additional 10-second intervals, kneading until smooth. Cut a small hole in corner of bag; squeeze to drizzle over madeleines. Allow chocolate to cool and set before serving.