Preheat oven to 350°F and generously grease a donut baking pan.
In a small bowl, whisk together flour, baking powder, and salt. Set aside.
In another bowl, cream together peanut butter and brown sugar, then whisk in egg and 1/2 cup milk.
Stir in flour mixture until incorporated. The batter will be very thick.
Divide batter among wells in donut pan.
Bake for 12-14 minutes, until lightly browned. Remove from pan immediately and let cool on wire rack.
When the donuts have cooled, mix together the glaze. Whisk together powdered sugar, jam, and remaining 2 tablespoons milk until you have a smooth glaze, adding more sugar or milk as necessary to achieve the consistency you like.
Dip the donuts in the glaze on one side and return to the wire rack. Sprinkle chopped peanuts on top.