1. Process flour, butter, curry powder, salt and egg in a food processor for a few seconds until the mixture becomes crumbly : do not process too much as the dough should remain crumbly.
2. Transfer the dough onto a work surface. Gather it into a ball shape of dough with hands.
3. To roll the dough: Put a plastic wrap covering on your work surface, place the dough on it. Then cover with another piece of plastic wrap. Roll the dough out into a circle shape bigger than your tart mold. Then place it gently into your tart mold. Using a sharp knife, trim the edges of the pastry to fit the tart pan. Prick the bottom and side of the tart thoroughly with a fork. Put it in the refrigerator or freezer until firm (about 30 minutes).
4. Preheat oven to 180C degree. Now that the dough is harder, line the tart with parchment paper or aluminum foil and fill it with pie weights/dried beans.
5. Bake for 25 minutes and then remove the parchment and weights. Continue to bake for another 5 min at 180C degree or until the dough is just beginning to brown lightly. Cool on a wire rack until needed.
6. Meanwhile prepare the filling : In a skillet add 1 tbsp vegetable oil, fry the garlic until fragrant. Add leek and cook until leeks are caramelized and golden brown. Season with ingredient A and stir for a few more minute. Remove the heat and let cool to room temperature.
7. Spread the cold leeks over the pastry, then sprinkle grated cheese evenly. Preheat the oven to 180C° degree.
8. In a bowl, whisk together Ingredient B (eggs, heavy cream and yogurt). Season with salt and pepper, then pour the egg mixture gently over the leeks.
9. Bake in the preheated oven for 30 minutes or until the top turns nicely golden.