Preheat the oven to 350F degrees. Spray a 6 cavity doughnut pan with non-stick cooking spray.
In a large bowl whisk together the flour, baking soda & salt. Set aside.
In a second medium-sized bowl whisk together the egg, melted butter, milk, yogurt/sour cream, instant coffee powder, vanilla & packed brown sugar. Make sure the coffee powder has dissolved and there are no sugar clumps.
Fold the wet ingredients into the flour mixture using a large wooden spoon or rubber spatula, then give the batter a quick whisk to ensure everything is well mixed. Spoon the batter into the prepared doughnut pan. Or pour/spoon the batter into a large ziplock bag, cut off the bottom corner of the ziplock bag, then pipe the batter into the doughnut pan. Fill each cavity to about ⅔ full - you should get about 6 to 8 doughnuts total.
Bake for 8-10 minutes, or until the doughnut feels slightly firm when touched gently with your finger tips. Allow to cool in the pan for 5-10 minutes, then remove from the pan and continue cooling on a wire rack.
While the doughnuts are cooling, make the glaze. Add all the ingredients to a double boiler and melt together over low heat while stirring occasionally. Alternately, add all the ingredients to a microwave-safe bowl and melt in 30 second bursts while stirring after each. Once everything is melted, whisk together until smooth.
Dip the tops of the doughnuts in the glaze, and optionally decorate with chocolate sprinkles.