- Preheat oven to 400°F. Line 12 muffin cups with paper liners; spray liners with nonstick spray.
- Combine all-purpose flour, whole wheat flour, brown sugar, oats, wheat germ, cinnamon, baking powder, ginger, and salt in medium bowl.
- Whisk together buttermilk, egg, oil, and vanilla in small bowl. Add buttermilk mixture to flour mixture, stirring just until blended. Gently stir in mangoes.
- Fill muffin cups evenly with batter. Bake until toothpick inserted in centers of muffins comes out clean, 18-21 minutes. Cool in pan on wire rack 5 minutes. Remove muffins from pan and cool on rack. Serve warm or at room temperature.
Mangoes are available year-round, but one of the best varieties, the juicy, jam-sweet Alphonso, is available from mid-April through May. Other excellent late-spring varieties to seek out are Haitian and Ataulfo.