For the pastry: 1) In a medium bowl, beat the oil, sugar and egg until creamy. In a separate bowl, combine the wholemeal and plain flours. 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.
2) Preheat oven to 180°C/ gas mark 4. Spray a mini muffin tin or tartlet pan with cooking spray.
3) Roll the pastry dough into a 1/2-cm thick sheet. With a biscuit cutter or small glass, make 24 rounds, about 5.5cm 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 three days in advance and store them in the refrigerator in an airtight container.
For the filling: 1) Put the yoghurt in a strainer lined with a paper towel. Place the strainer over a bowl and put in the refrigerator to drain and thicken for at least four hours and up to eight hours.
2) Transfer the drained yoghurt from the strainer to a small bowl. Discard the liquid.
3) Fill each tartlet with one teaspoon of thickened lemon yoghurt. Place about two teaspoons of diced mango, two slices of kiwi fruit and a mint leaf on top of each tartlet. Sprinkle with icing sugar.