How to Make It
Sift the flour and salt into a bowl. Make a well in the center of the flour and add 2/3 cup (150 milliliters/5 fluid ounces) cold water. Mix to form a firm dough, then add the olive oil and knead for 5 minutes, until the dough is soft and elastic, dusting with more flour if necessary. Wrap in plastic wrap (clingfilm) and let rest for 30 minutes in a warm place.
Cut most of the dark green tops from the leeks, halve the leeks lengthwise, and slice them 1/4 inch (5 millimeters) thick. Transfer the slices to a bowl, add the tofu and chili powder, season to taste with salt and freshly ground black pepper, and stir in the vegetable oil.
Roll out the dough into a large rectangle and, using a 3 1/4–4-inch (8–10 centimeters) round metal cutter, cut out circles.
Place 2 teaspoons of the leek filling in the center of a dough round. Using your finger, wet the edges of the dough and fold the dough over the filling, pressing the edges together to seal well. Using a fork, crimp the edge to seal the semicircle tightly. Repeat with the remaining dough circles and filling.
Heat the oil for deep-frying in a large saucepan over low heat. Line a plate with paper towels.
Carefully drop batches of 4–5 of the patties into the hot oil and deep-fry gently for 4–5 minutes, until golden. Drain on the paper towel–lined plate and serve hot or warm with your favorite dipping sauce.