1) Preheat the oven at 375°F.
2) Make four portions of blueberries. Leave four blueberries for garnish.
3) Mix together flour and butter till the mixture feels like course cornmeal.
4) Add in sugar, cover and refrigerate it till needed.
5) Butter four au gratin dishes, put each portion of blueberries, cover each with the crumble mix. Bake it for 20 minutes.
6) Remove and cool
7) Serve at room temperature. Garnished with a blueberry on top.