PREHEAT oven to 375º F. Grease or paper-line 18 muffin cups.
COMBINE baking mix, flour and sugar in large bowl. Add eggs, yogurt, juice and orange peel; stir just until blended. Stir in 1 1/3 cups morsels. Spoon into prepared muffin cups, filling 3/4 full. Sprinkle with nuts.
BAKE for 18 to 22 minutes or until wooden pick inserted in center comes out clean. Cool in pans for 10 minutes; remove to wire racks to cool slightly.
MICROWAVE remaining 1/3 cup morsels in small, heavy-duty plastic bag on MEDIUM-HIGH (70%) power for 1 minute; knead. Microwave at additional 10- to 15-second intervals, kneading until smooth. Cut tiny corner from bag; squeeze to drizzle over muffins. Serve warm.