Banana Pineapple Streusel Muffins

Streusel Topping:

1/2 cup sugar
1/3 cup all-purpose flour
1/2 teaspoon ground cinnamon
1/4 cup (1/2 stick or 4 Tablespoons) cold butter, cut into 1/2-inch square chunks

Batter:

Preheat oven to 350 degrees F. Grease loaf pan(s) and/or muffin tins (or line with muffin papers).

Streusel Topping:

Place sugar, flour, cinnamon, and cold butter in the bowl of a food processor fitted with the metal blade. Pulse until mixture resembles coarse crumbs. Do not over-process. (You may also do this by hand using a pastry cutter.) Set aside.

Batter:

Combine flour, sugar, salt, baking soda, and cinnamon in a large bowl. Stir in pecans or walnuts. Set aside.
In a medium bowl, combine mashed bananas, drained crushed pineapple, beaten eggs, oil, and vanilla extract. Add to flour mixture, stirring with a wooden spoon just until dry ingredients are moistened. Do not overstir!
At this point, I use the batter for not only muffins, but also a medium-sized loaf. You can use it as you wish, of course. Spoon batter into a greased and floured loaf pan. Sprinkle 1/2 of streusel mixture over the top of the loaf. Bake at 350 degrees F. for about 1 hour or until a wooden pick inserted in the center comes out clean. Cool in pan for 10 minutes, then remove from pan and let cool on wire rack.
Increase oven temperature to 375 degrees F. Use remaining batter for your favorite-sized muffins, filling paper-lined muffin tins a little more than half full. Sprinkle tops with remaining streusel mixture. Bake about 25 to 30 minutes for regular muffins, and about 15 to 18 minutes for mini-muffins. Let cool for 10 minutes, then remove and finish cooling on wire racks.