Preheat the oven to 375°F. In a mixing bowl, combine the ground pork, grated apple, sage, breadcrumbs, egg, onion, salt, and pepper. Mix until evenly blended.
Divide the mixture into four equal portions and shape each into a mini meatloaf. Arrange them on a baking sheet.
Bake for 25 minutes.
While the meatloaves bake, place the potatoes in a large pot, cover with water, and bring to a boil. Cook until tender, then drain.
Mash the potatoes with the milk, 2 tablespoons of butter, and the additional salt until smooth.
Remove the meatloaves from the oven. Spread the mashed potatoes evenly over each loaf and dot the tops with the remaining tablespoon of butter.
Return to the oven for 10 minutes until the potato topping begins to brown.