Heat 2 tbsp. olive oil in a large saucepan over medium-high heat. Add the lamb (you may need to do this in 2 batches so as not to overcrowd the pan) and cook for 5-7 minutes, stirring often, until the color has changed from red to brown. Transfer lamb to a plate, keeping juices in the pan.

Add onion and garlic, and cook for 3-5 minutes until translucent. Add kumara and Dish Delicious, and stir to coat. Cook for an additional 3-5 minutes until fragrant and onion is beginning to brown.

Add the lamb back into the pan ,Sprinkle over flour, then add  Vegetable stock or beef stock and balsamic vinegar. Bring to a boil, then reduce heat to medium-low. Simmer, covered, for 35 minutes, then remove lid and cook for another 15 minutes. Stir through sultanas and salt, and remove from the heat.

Preheat oven to 180°C and grease a deep 23cm pie dish. Roll out pastry dough to create a crust and lid for the pie. Line the pie dish with the crust, leaving a bit of overhang around the edges. Fill with the lamb sauce , then place the pastry lid on top. Fold up the edges and seal with a little water. Cut 2 slits in the top to allow steam to escape. Brush with oil, and bake for 40 minutes until pastry is nicely browned and crisp.

Serve hot, and reheat leftovers in the oven.