Preheat oven to 350°.
Mix sugar, oil and eggs.
Add pumpkin and vanilla bean paste and stir well.
Add flour and remaining ingredients; stir only until combined. (If over mixed bread will become tough and rubbery.)
Spoon the batter into the prepared muffin cups, filling each one nearly to the brim.
To make the crumb topping, mix together the flour, granulated sugar, brown sugar, and pumpkin pie spice in a small bowl.
Add the melted butter and use a fork to mix until crumbly—be careful not to over mix —mix just until combined.
Sprinkle the crumb topping evenly over the batter in the muffin cups, pressing it down lightly.
Bake at 350 degrees for 20 to 25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for 10 minutes while you prepare the icing.
For the icing, simply whisk all the ingredients together until you achieve a smooth consistency. Drizzle the icing over the muffins while they’re still warm. Store any leftovers in an airtight container at room temperature for up to 2 days, or refrigerate for up to a week.
If you want to freeze the muffins for later, they can be stored with or without the icing for up to 3 months. To serve, thaw them in the refrigerator overnight, then bring them to room temperature or warm them in the microwave. Add the icing after thawing, if needed.
For mini muffins, adjust the baking time to 11-13 minutes at 350°F (177°C).