Preheat oven to 350°F. Line a muffin tin with liners and set aside.
In a mixing bowl, sift together the flour, baking powder, baking soda, cinnamon, nutmeg, cloves, and salt. Set aside.
In another mixing bowl, whisk together the egg, sugars and oil. Stir in the squash, banana, milk, and vanilla extract until fully incorporated. Pour the dry mixture into the wet mixture and stir until just combined.
Pour the batter into the liners and fill each about ⅔ full.
For the streusel: Combine the butter, sugar and flour in a small mixing bowl and cut together, using a pastry knife or he back of a fork. (the end result should have a very fine, grainy texture)
Sprinkle a generous amount of streusel over the top of each muffin, about 2 tablespoons.
Bake for about 20-25 minutes or until a toothpick comes out clean when inserted into the center of the muffins.
Allow to cool for about 20 minutes before serving.