Heat oven to 350. Spray 16-18 muffin cups w/ cooking spray. In bowl, whisk together flour, baking powder, baking soda, sugar, cinnamon, ginger, nutmeg and salt.
In lg bowl, beat pumpkin,1 stick melted butter, eggs and vanilla. Add dry ingredients to wet ingredients until just combined.
In small bowl, combine 2 tbsp butter, 1/4 cup sugar, 1/4 cup flour, and 2 tsp cinnamon w/a fork until crumbly. Fill muffin cups 2/3 full w/ batter. Sprinkle 1 tbsp struesel mix on top of batter. Bake 20 mins, or until a toothpicl inserted in center comes out clean. Let cool. In another small bowl, whisk together 1 tbsp melted butter, powdered sugar and milk. Drizzle over cooled muffins, or dip the top of each muffin in frosting.