• Preheat oven to 400°F/200°C. Line muffin tins with papers or spray muffin compartments with vegetable spray.

Crumble Topping

• In a bowl stir together the sugar, cinnamon, and flour. Drizzle with vegan butter and stir to combine until you achieve a crumbly mixture. Don't overmix. Set aside.

Muffins

• In a medium bowl stir together the oil, sugars, applesauce, milk, and vinegar. Stir to combine.
  
• In a large bowl stir together the flour, cornstarch, baking powder, baking soda, cinnamon, and salt. Create a well in the middle of the flour. Pour the milk mixture in and stir until just combined.
  
• Pour the batter into prepared muffin tins. Use a spatula to get every last bit of the batter. Spoon the crumble topping evenly across the muffins. Use your hand to gently tamp down the crumble topping. Bake for 5 minutes, then leaving muffins in the oven, turn the oven temperature down to 350°F/175°C. Bake for another 16 - 17 minutes until a toothpick inserted in the middle comes out clean. The crumble topping should be nice and golden brown as well.
• When done, remove from the oven and allow to cool for 10 minutes before drizzling with icing.

For the Icing Drizzle

• Prepare the icing by adding powdered sugar to a bowl. Add milk and whisk.
• Store muffins in an airtight container at room temperature for up to 3 days. These muffins can be refrigerated up to 7 days or frozen for up to 1 month.