Preheat the oven to 350°F (177°C). Grease two donut pans with cooking spray or grease it with butter.
In a medium mixing bowl, whisk together the flour, baking soda, salt and baking powder. Set aside.
In a large mixing bowl, whisk together the egg, granulated sugar, vegetable oil, sour cream, and vanilla extract.
With a wooden spoon, or spatula, stir in the flour mixture and stir until just combined. Do not overmix.
Fold in the chopped strawberries and combine.
Fill each cavity of the prepared donut pan about 2/3 full. You can spoon the batter in, or fill a piping bag and pipe the batter into the pans.
Bake for 13-15 minutes or until the doughnuts are golden brown. Cool the doughnuts in the pan for 5 minutes before transferring them to a cooling rack to cool completely.
In a small bowl, combine the crushed strawberries and the powdered sugar until you get a thick glaze. The glaze should slowly drip off the end of the spoon in a thick ribbon.
Dip each doughnut about halfway into the glaze. Allow the excess to drip off. Place the doughnuts back on the cooling rack and let them set for 10 minutes.