Preheat oven to 375°F (190°C). Place peeled, cubed potatoes in a pot of cold salted water. Bring to a boil and simmer for 15-20 mins until tender.

Heat olive oil in a skillet. Sauté onion and carrot until soft, 5-7 mins. Add garlic and cook 1 min more. Let cool.

In a small bowl, make the glaze by whisking ketchup, brown sugar, and vinegar. Set aside.

In a large bowl, combine panko and milk to make a panade. Add beef, cooled veggie mix, egg, Worcestershire, tomato paste, thyme, paprika, 1 tsp salt, and 1/2 tsp pepper. Mix gently with hands until just combined.

Press meat mixture evenly into a greased 12-cup muffin tin. Bake for 15 mins.

Remove muffins from oven and spoon glaze over each one. Return to oven for 5-10 mins, or until internal temp reaches 160°F (71°C).

Drain potatoes well. Rice or mash until smooth. Mix in butter, then warm milk and sour cream until creamy. Stir in cheese (if using). Season with salt and white pepper.

Let muffins cool for 5 mins, then remove from tin. Pipe or spoon mashed potatoes on top. Garnish with parsley and serve.