Heat oven to 400°F (375°F for dark or nonstick pan). Spray bottoms only of 12 regular-size muffin cups with cooking spray or place paper baking cup in each muffin cup.
Set aside streusel packet from muffin mix. In large bowl, stir muffin mix, ginger and nutmeg. In medium bowl, beat eggs with fork. Stir in orange juice concentrate, milk and oil. Stir in carrots and 1/2 cup of the walnuts. Using rubber spatula, fold wet ingredients into dry ingredients just until moistened (batter may be slightly lumpy; do not overmix).
Divide batter evenly among muffin cups, using 1/4 cup for each. (If any carrots are sticking out of batter, push in with finger.) Sprinkle reserved streusel over batter; top with remaining 1/2 cup walnuts. Bake 17 to 22 minutes or until golden brown and toothpick comes out almost clean. Cool 10 minutes; remove from pan to cooling rack.