1In large bowl, mix Muffin Mix ingredients. Spoon into jar with lid or resealable food-storage plastic bag; cover jar or seal bag. In another jar or bag, mix Streusel Mix ingredients; cover or seal.
2To make muffins, heat oven to 375°F. Line 12 regular-size muffin cups with paper baking cups or spray bottoms only of muffin cups with cooking spray. In large bowl, mix Muffin Mix, water, oil and egg with spoon just until dry ingredients are moistened. Spoon batter evenly into muffin cups.
3In small bowl, mix Streusel Mix with melted butter. Sprinkle mixture evenly over batter in cups; press in lightly.
4Bake 14 to 18 minutes or until toothpick inserted in center comes out clean. Remove from muffin cups; serve warm.