1. Preheat oven to 400°F. Line twelve 2 1/2-inch muffin cups with paper bake cups; set aside.

2. In a large bowl stir together flour, baking powder, and salt. Stir in chocolate pieces. Make a well in the center of flour mixture; set aside.

3. In a medium bowl combine eggs, sugar, milk, orange peel, orange juice, and oil. Add egg mixture all at once to flour mixture. Stir just until moistened (batter should be lumpy).

4. Spoon 1/4 cup of the batter into each prepared muffin cup. Sprinkle generously with Streusel Topping. Bake for 18 to 20 minutes or until a wooden toothpick inserted in centers comes out clean.

5. Cool in muffin cups on a wire rack for 5 minutes. Remove from muffin cups; serve warm.

Streusel Topping

1. In a medium bowl stir together flour and sugar. Using a pastry blender, cut in butter until mixture resembles coarse crumbs. Stir in walnuts and chocolate pieces.