Preheat your oven to 375°F (190°C).

Line a 12-cavity muffin pan with muffin papers.

In a bowl, stir together the ingredients for the streusel topping: flour, brown sugar, white sugar, and cinnamon until there are no lumps.

Add the melted butter to the dry mixture and stir until it looks like damp sand. Set aside.

In a separate bowl, whisk together flour, pumpkin pie spice, cinnamon, baking powder, baking soda, and salt.

In a large bowl, combine oil, brown sugar, white sugar, eggs, vanilla extract, sour cream, and pumpkin puree. Whisk until smooth.

Gradually add the dry ingredients to the wet ingredients in two batches, mixing until there are no lumps.

Spoon the batter into the muffin cavities, filling each about three-quarters full.

Sprinkle the streusel mixture on top of each muffin.

Bake for 22 to 25 minutes. Check doneness with a toothpick.

Cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

Whisk together the powdered sugar and cream until smooth, and drizzle over the cooled muffins.