- Preheat the oven to 200°C/gas mark 6. Grease a 12-cup muffin tin liberally and line a baking tray with non-stick baking paper.
- Heat the oil in a large sauté pan set over a medium heat. Add the celery, carrot, onion and garlic and fry for 6 to 8 minutes, until the veg are starting to soften.
- Remove to a bowl, then add the beef mince to the pan, breaking it up with a wooden spoon. Fry until brown, then add the vegetables back to the pan along with the stock, tomato purée and Worcestershire sauce.
- Simmer for 15 to 20 minutes, until the liquid has been soaked up. While the mince is cooking, mix the sweet potatoes and eggs together in a medium-sized bowl, then season with salt and pepper.
- Add 3 tablespoons of this mixture to each muffin cup. Shape using your fingers or a teaspoon to make a nest in the middle, bringing the sweet potatoes up the sides of each cup.
- Bake in the oven for 15 minutes, then remove from the tin and place on the lined tray. Divide the mince between the cups and sprinkle with the cheese.
- Return to the oven for a further 8 to 10 minutes, until the cheese is golden and melted. Serve warm.
Time-saving tip:
If you cook the mince the day before, you should reheat it before you place it in the shells. By making the mince the night before, you also give the flavours a chance to infuse.