Turn dough onto a lightly floured surface.
Roll to ⅜ inch thick.
Use a 3 inch cutter to cut dough into rounds.
Place on sheet pans covered in parchment.
Cover and allow to proof while oil heats.
Pour 2-3 inches of oil in a large dutch oven.
Heat to 350℉/177℃.
Add doughnuts in batches of not more than 4.
Cook 3-4 minutes per side, or until golden brown and cooked through.
Drain.
Immediately roll in strawberry sugar.
Set aside to cool.
When cool, spoon strawberry jam into piping bag fitted with bismark tip.
Pipe into center of each doughnut.