- In a food processor, pulse the flour, brown sugar, baking powder and salt. Add the butter and pulse until the butter is the size of peas. Add the egg and yogurt. Pulse until the dough just starts to hold together. Add water if necessary. Remove the dough from the food processor and shape into a log. Wrap in plastic wrap. Refrigerate for 30 minutes.
- With the rack in the bottom position, preheat the oven to 200°C (400°F). Line a baking sheet with parchment paper.
- In a bowl, combine the brown sugar and flour. Add the butter and mix well. Set aside.
- On a floured surface, cut the dough log into 8 discs. Roll them out to a thickness of about 3 mm (1/8 inch), making discs about 15 cm (6 inches) across. Spoon about 22.5 ml (1 1/2 tablespoons) of filling onto the middle of each disc and top with a peach half, cut side down. Brush the circumference with milk. Fold the dough toward the centre, partially covering the peaches and crimping to make folds.
- Arrange the tartlets on the baking sheet. Brush with the remaining milk and dust with sugar. Bake for about 25 minutes.