For The Dough For The Filling

1. Combine plain yogurt, vegetable oil, and ½ tsp salt in a bowl to make the dough. In a separate bowl, whisk together flour and baking powder.
2. Add wet ingredients to dry ingredients and mix with a spatula until a dough forms. Cover and refrigerate for 30 minutes.
3. While the dough is resting, boil potatoes for 10-12 minutes or until tender when pierced with a fork. Drain, rinse, and mash potatoes.
4. Heat vegetable oil in a large skillet over medium-high heat. Sauté spring onions for 2 minutes. Add mashed potatoes, spinach, ½ tsp each of salt and pepper. Cook, stirring occasionally, until spinach wilts.
5. Transfer dough to a floured surface and divide into 8 equal pieces. Roll each piece into a 10-12cm circle and place 2 tbsp of filling in the center of each. Fold dough over the filling to enclose it, gently flatten with your palm, and crimp the edges with your fingers. Optionally, you can braid the edges or press them down with a fork.
6. Heat olive oil in a large skillet over medium-high heat and pan-fry the piroshkis for 3-4 minutes per side or until golden brown and crispy. Allow to cool for 2-3 minutes before serving.