Preheat oven to 350 degrees (F). Spray a 6 mold donut pan with non-stick baking spray; set aside.
For the Crumb Topping:
In a small bowl combine the sugar, flour, and pumpkin spice. Add in the melted butter and use a fork to stir it into a coarse meal. Chill the topping in the freezer while making the donut batter.
For the Pumpkin Donuts:
In a large bowl combine the flour, brown sugar, salt, baking powder, and pumpkin spice; mix well, making sure any large clumps of brown sugar gets broken up; set aside. In a separate bowl whisk together the pumpkin puree, melted butter, and milk. Gently fold the wet mixture into the dry mixture - don't over mix!
Spoon or pipe the mixture into prepared doughnut pan. Divide crumb topping evenly among donut tops, then bake for 10-11 minutes, or until the doughnuts spring back when lightly pressed. Allow doughnuts to cool for 10 minutes in the pan before gently lifting them out and transferring to a wire wrack to cool for a few more minutes.
For the Pumpkin Spice Glaze:
In a small bowl whisk together the confectioners' sugar, milk, vanilla, and pumpkin spice. Drizzle over donuts and serve at once.