1. Preheat oven to 180°C (360°F). Tear off four large squares of aluminium foil and place one sweet potato on each. Season each sweet potato with sea salt and drizzle with a little with extra virgin olive oil.
2. Use a fork to prick each potato several times then wrap lightly with foil. Place in the oven on a baking tray and bake for approximately 1 hour.
3. While sweet potatoes are cooking, heat remaining olive oil in a non-stick frypan (low-medium heat). Sweat leeks until soft, but not coloured. Add garlic and artichoke and cook on low heat for a further 3-5 minutes. Remove from heat and set aside to cool.
4. Use a skewer to carefully check if sweet potatoes are cooked through. Remove from the oven, carefully unwrap aluminium foil and set aside to cool slightly.
5. Once sweet potatoes are cool enough to handle, cut each one in half and place back on the baking tray. Carefully scrape out the flesh of each half with a small spoon, leaving a thin layer of potato inside each skin.
6. Add the flesh to a medium-size bowl and roughly mash with a fork or potato masher. Add leek and artichoke mix, 2 tablespoons of fresh herbs, goat’s cheese, 1/2 cup cheese, sea salt and pepper. Mix well to combine.
7. Preheat grill. Divide filling into each of the sweet potato skins. In a small bowl, mix together sourdough bread crumbs, remaining cheese and remaining chopped herbs.
8. Top each sweet potato half with a little of the mixture and broil under the grill for about 3 to 5 minutes, or until the topping is lightly toasted.
Serve with a fresh leafy green salad.