Place the yogurt in a strainer lined with a paper towel. Put the strainer over a bowl and place in the refrigerator to drain and thicken for at least 4 hours and up to 8 hours.
In a medium bowl, beat the oil, sugar and egg until creamy. In a separate bowl whisk together the whole-grain pastry flour and the all-purpose flour. Gradually add the flour mixture to the egg/oil mixture, stirring, until they are combined and a soft dough is formed. Roll the dough into a ball and refrigerate for 30 minutes.
Preheat oven to 350 degrees F. Spray a mini muffin tin or tartlet pan with cooking spray.
Roll the pastry dough into a 1/8-inch thick sheet. With a biscuit cutter or small glass make 24 rounds, about 2 1/2 inches in diameter. Place rounds in the pan and bake for 15 minutes, or until crisp. Remove tartlets from oven and set aside to cool completely. You can make the shells up to 3 days in advance and store them in the refrigerator in an airtight container.
Transfer the drained yogurt from the strainer to a small bowl. Discard the liquid. Fill each tartlet with 1 teaspoon of thickened lemon yogurt. Place about 2 teaspoons of diced mango and 2 slices of kiwi and a mint leaf on top of each tartlet. Sprinkle with confectioners' sugar. Serve immediately after filling.