Whip heavy cream with an immersion blender or electric mixer with powdered milk and powdered sugar, until it's thick and peaks form when the whisk attachment when pulled away.
The powdered milk with help keep the whipped cream from getting "watery" it stays well for days in the fridge.
This can be spread over the cake, then add sprinkles. Refrigerate and take out 20-20 mintus before serving for best flavor of cake and frosting.