In a medium bowl, whisk together the brown sugar, granulated sugar, cinnamon, and salt. Add the melted butter and stir with a rubber spatula until combined. Add the flour and mix just until moist clumps form. Set aside.

Preheat your oven to 375°F. Line a standard 12-cup muffin pan with paper liners.

In a large bowl, whisk together the eggs, granulated sugar, brown sugar, pumpkin puree, and vegetable oil until smooth and well combined.

Add the flour, baking soda, baking powder, pumpkin pie spice, and salt to the wet mixture. Stir with a spatula just until no dry streaks remain. Do not overmix.

Divide the batter evenly among the prepared muffin cups, filling each about three-quarters full. Generously spoon the streusel topping over the batter, mounding it slightly and pressing down gently to help it stick.

Bake the muffins at 425°F for 7 minutes, then reduce the oven temperature to 350°F and continue baking for 10 to 12 minutes, or until a toothpick inserted into the center of a muffin comes out with a few moist crumbs. Let the muffins cool in the pan for 15 minutes, then transfer them to a wire rack.

While the muffins cool, whisk together the powdered sugar and milk in a small bowl until smooth. Place a sheet of parchment paper under the wire rack, then drizzle the icing over the warm muffins.