Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan with the olive oil.
Place the grated apple in a clean kitchen towel and gently squeeze out excess juice. This helps the muffins hold their shape while staying moist.
In a large bowl, combine the ground pork, squeezed apple, egg, almond flour, onion, sage, Dijon mustard, salt, and pepper. Mix gently with your hands or a fork just until evenly combined.
Divide the mixture among the 8 greased muffin cups. Press it in lightly, leaving the tops slightly mounded.
Bake until the centers are cooked through and the tops are lightly browned, about 25 to 30 minutes. Let the muffins rest in the pan for 5 minutes, then carefully lift them out to serve.