In a small, microwave-safe bowl, melt butter in the microwave and set aside to cool slightly.
In small bowl, whisk together flour, baking powder, cinnamon, ginger, nutmeg, cloves, and salt.
In a large bowl, combine pumpkin puree, brown sugar, egg, milk, and slightly cooled melted butter. Whisk until well-combined.
Add flour mixture to the pumpkin mixture and use a spoon to stir until just mixed.
Transfer batter to a piping bag (or disposable plastic bag and cut off one of the corners) and pipe batter into the prepared donut pan, filling rings 3/4 of the way full—this should make exactly 6 donuts.
Take streusel out of the refrigerator and crumble mixture over the top of the batter, being careful not to break up the streusel too much.
Bake for 9 to 11 minutes, until a toothpick inserted into the center of the donuts comes out with just a few moist crumbs or the tops of the donuts just spring back when pressed with a finger.
Cool the donuts in the donut pan until cool enough to handle and then gently remove each donut and transfer to a cooling rack. Cool for about 15 minutes before glazing.