Heat the oil in a large frying pan over medium-high heat, then sear the pork for 3 to 4 minutes on each side. Remove the pork from the pan and place it inside a deep casserole dish. Add the onion, carrot, celery and apple to the same frying pan and sauté for 4 to 5 minutes until the onions begin to sweat and become slightly translucent. Add the garlic and season with salt and pepper, stirring well. Incorporate the tomato paste and stir. Add the garlic powder, onion powder, chilli powder, and smoked paprika, continuing to sauté for 3 to 4 minutes. Deglaze the pot with the red wine, scraping any brown bits from the bottom. Reduce the heat to medium and simmer until about half of the wine has evaporated. Add the chopped tomatoes and beef stock, and let the mixture simmer.
Once it reaches a simmer, gently pour the mixture over the seared pork in the casserole dish. Cover and place on the lowest shelf in the oven. Braise the pork for about 2 hours or until fork-tender. Remove the pot from the oven and finely shred the pork with two forks. Taste and adjust the seasoning if needed.
Bring a saucepan of water to a boil and blanch the sliced potatoes until soft yet slightly firm. Thinly slice the apples slightly thicker than the potatoes, keeping them round. Place both the potatoes and apples in a bowl and add the melted butter, gently folding to coat. Add salt and pepper to season. Layer the potato and apple slices on top of the casserole dish, alternating between the two. Place into the oven to bake under the topping is golden brown.
Heat the olive oil in a frying pan until shimmering. Add the sage leaves in a single layer and fry for about 30 seconds until crisp. Remove with a slotted spoon and place on a paper towel-lined plate.
Remove the pie from the oven, garnish with grated Parmesan and fried sage leaves and serve.
