Whisk together flour, salt, and turmeric. Cut in butter and coconut oil with a pastry blender or hands until mixture looks like coarse meal. Incorporate yoghurt and water with a fork, stirring just until all flour is moistened. Bring dough together in a ball, wrap tightly, and chill for at least 40 minutes.
Once dough has chilled, half the dough and place one half on a well-floured work surface. Roll dough out to 1/8 inch thickness. Using a 3" biscuit cutter ( you can also use 3 inch drinking glass or lid) cut out 8 circles. You will need to reform scrap pastry and roll out again to get all the circles. Repeat this process with the 2nd half of dough.
Place pastry circles on a parchment lined baking sheet and refrigerate for (at least) 20 minutes. Meanwhile, place butter in a saucepan over medium heat. When butter has browned a bit, add garlic, apple, and leek. Cook down for 2-3 minutes, then add curry powder. Season to taste with salt and pepper and remove from heat.
Place a heaping tablespoon of apple mixture onto 8 pastry circles, then top each one with another circle that will come down over the filling-making sure to tightly seal the seams with a fork. Refrigerate filled pastries for 20 minutes. Preheat oven halfway through chilling time.
Bake hand pies at 375 for 22-24 minutes. Crust should be a vibrant golden brown and flaky on both sides. Let cool on rack for 5 minutes before consuming.
*Optional: mix together egg yolk and 2 tbsp water. Use a pastry brush to gently wash filled pastries before baking. This encourages even browning.