Spiralize your sweet potatoes using a spiralizer. Heat the oil in a large skillet over medium heat and add the sweet potato noodles. Season them with garlic powder, salt and pepper. Cook 8-9 minutes until they start to soften. Transfer the noodles to a bowl and let them cool for a few minutes. Beat the egg and mix it into the noodles.
Place the sweet potato noodles into the cups of a 12-cup muffin pan, forming nests. Press them in firmly, compacting them well. Place the muffin pan in the freezer for 15-20 minutes to allow the nests to firm up.
Line a baking sheet with foil and spray with olive oil. Place the sweet potatoes on the baking sheet and spray the tops with olive oil. Bake in the oven until sweet potatoes are cooked through and tops start to brown, about 12 minutes. Remove from oven.
Transfer the sweet potatoes onto a serving platter. Top each one with a slice of mozzarella and some tomatoes. Drizzle each with about ½ teaspoon of balsamic reduction and garnish with fresh basil.