Preheat the oven to 350° F. Grease doughnut pan(s) with butter or cooking spray.
In a bowl, mix the flour, sugar, baking powder, and salt.
In another bowl, beat the eggs. Add the butter, milk, and vanilla.
Add the wet ingredients to the dry ingredients and mix until smooth. If the mixture is too thick, thin it out with a little more milk.
Fill a plastic bag (or pastry bag, if you have one) with the dough. Cut a hole in the corner, and pipe the dough into the doughnut pans. Fill them about half to three-quarters of the way; they will rise.
Bake for 13 to 15 minutes or until lightly golden brown.
Remove from the oven and let the doughnuts cool in the pans for at least 5 minutes. When cool enough to handle, transfer the doughnuts to racks to finish cooling.
Ice the doughnuts with grape or blueberry jelly, blue frosting, or both. Then, dip them into the cookie streusel topping. Dust with more powdered sugar before serving, if desired.
Makes 12 doughnuts.