Mango Coffee Cake

Topping:1/2 cup brown sugar
1/4 cup sifted all-purpose flour
1/4 cup butter, room temperature
1 teaspoon cinnamon
1/4 cup chopped nuts (optional)
.
Cake:
1 1/2 cups sifted all-purpose flour
2 1/2 teaspoons baking powder
1/2 teaspoon salt
1 egg, beaten
3/4 cup sugar
1/3 cup melted butter or vegetable oil
1/2 cup milk
1 teaspoon vanilla extract
1 small under ripe mango

Topping 

1. In small mixing bowl, combine topping ingredients. Blend with fork until crumbly. Set aside.

 2. Sift 1 1/2 cups sifted flour with baking powder and salt into a bowl.

3. In a medium bowl, beat together beaten egg and 3/4 cup sugar and 1/3 cup melted butter or oil. 

4. Add milk and vanilla. Stir in flour mixture and mix well.

5. Pour half batter into a a greased and floured 8-inch square or 9-inch layer-cake pan. . Sprinkle mangoes over batter.Pour remaining batter over mangoes.

 6. Sprinkle topping crumb mixture evenly over batter.

Bake at 375° for 25 to 30 minutes, or until cake tests done. Partially cool in pan on wire rack. Cut coffee cake into squares while still warm.