How to Make It
Preheat the oven to 375° F. Divide the frozen berries among 4 small (1 cup) gratin dishes or custard cups. Toss the crumbled shortbread and sugar together in a small bowl. Divide the crumbs among the gratin dishes, sprinkling them on top of the berries, and dot with the butter. Arrange the dishes on a cookie sheet and bake for 16 to 18 minutes. Let cool to lukewarm or room temperature and serve with sour cream.