Heat 3 tablespoons (60ml) of olive oil over medium heat in an oven-safe frypan, and cook and stir the onion and garlic until translucent, about 5 minutes. Stir in the green capsicum and cook and stir until it has begun to soften, 5 more minutes. Pour the eggs over the vegetables and stir in the basil, rosemary, salt and pepper. Reduce the heat to medium-low, let the eggs sit over the heat until they have started to set, about 10 minutes.
Transfer the frypan to the preheated oven and cook the frittata until fully set, about 15 minutes.
While the frittata is cooking, heat 1 cup (250ml) of olive oil in a deep-fryer or large saucepan to 190 degrees C. Deep-fry the sweet potato sticks, a layer at a time, until golden brown and crisp, about 5 minutes. Remove with a slotted spoon, and drain on paper towels. Top cooked frittata with the fried sweet potato slices to serve.