Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. This recipe makes 15 muffins, so prepare a second muffin pan in the same manner. Set aside.
In a large bowl, whisk the flour, baking soda, cinnamon, pumpkin pie spice, and salt together until combined. Set aside. In a medium bowl, whisk the oil, granulated sugar, brown sugar, pumpkin puree, eggs and milk together until combined. Pour the wet ingredients into the dry ingredients, then fold everything together gently just until combined and no flour pockets remain. Spoon the batter into liners, filling them almost full.
Whisk the flour, granulated sugar, brown sugar, and pumpkin pie spice together until combined. Using a fork, lightly mix in the melted butter until crumbs form. Don’t over-mix. Spoon crumbs evenly on top of the batter and gently press them down into the batter so they’re snug.
Bake for 5 minutes at 425°F (218°C) then, keeping the muffins in the oven, reduce the oven temperature to 350°F (177°C). Bake for an additional 16-17 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 21-22 minutes, give or take. Allow the muffins to cool for 10 minutes in the muffin pan as you make the icing. *For mini muffins, bake for 11-13 minutes at 350°F (177°C) the entire time. Whisk all of the icing ingredients together until combined and smooth. Drizzle over muffins and serve warm. Cover tightly and store at room temperature for 1-2 days or in the refrigerator for up to 1 week.
