1 1/2 cups all-purpose flour
3/4 cup sugar
1/2 teaspoon salt
2 teaspoons baking powder
1/3 cup butter, melted and cooled slightly
1 egg, lightly beaten
2/3 cup milk
1 1/2 cups fresh mango, diced
for the streusel topping
5 tablespoons unsalted butter, cold
1/2 all-purpose flour
1/3 cup light brown sugar, packed
1/4 cup raw macadamia nuts, toasted
1/4 cup crystallized ginger chunks
Preheat oven to 400F. Grease muffin cups or line with muffin liners.
Combine flour, sugar, salt and baking powder in one bowl. In another small bowl, combine melted butter, milk and egg. Mix this with flour mixture. Fold in blueberries. Fill muffin cups right to the top, and sprinkle with crumb topping mixture.
To make streusel topping: Place toasted macadamia nuts and crystallized ginger in food processor bowl. Pulse machine on/off until you get small, coarse pieces. Add butter, flour, and brown sugar to bowl. Using on/off pulse again, process together into even, large crumbs. Sprinkle over muffins before baking.
Bake for 20 to 25 minutes in the preheated oven, or until a toothpick come out clean and they are a golden brown.