Brown ground beef and onion in a large skillet over medium-high heat. Add the peas and carrots and continue to cook over medium heat for about 5 minutes; stir in the gravy, cover and set aside. It may be necessary to reheat this at the time of the assembly.

Preheat oven to 400F/200C. Scrub potatoes to remove all dirt and sand then dry with paper towels.

Rub each potato with a bit of butter or olive oil. Pierce each potato with a fork in several places so steam can escape. Bake approximately 1 hour or until potato feels 'soft' when gently squeezed. Remove from oven and let them cool until they can be handled.

Cut potatoes in half lengthwise then scoop out most of the potato leaving about 1/8-inch/0.3cm 'wall.' Place the scooped out portion in a bowl and mash with the milk and butter, using only enough milk to make creamy potatoes—the amount of milk is approximate.

Fill the scooped out potatoes with equal portions of the meat mixture then top each with an equal amount of the mashed potato. Sprinkle with paprika. Place on a baking tray.

Preheat broiler and broil until potato topping is just beginning to brown.