When the rhubarb season is in full swing, it's worth trying this simple recipe for a crispy oatmeal pie with a rhubarb filling! Ingredients Powdered sugar: 200 g Vanilla sugar: 2 packets Butter: 300 g Whole wheat flour: 400 g Rolled oats: 150 g Baking powder: 0.5 teaspoon Rhubarb filling…