Prepare Eggplants: Peel 3-4 lines into each aubergine, then rub them with salt and leave them to sit for 20 minutes to draw out bitterness.
Cook Vegetables: In a large pan, add 3 tablespoons of olive oil and heat over medium-high. Once hot, add the onions, diced bell peppers, and a generous pinch of salt. Stir well and cook for 2 minutes before adding the garlic. Continue cooking for an additional 5 minutes.
Cook Beef Mixture: Push the vegetables to the side of the pan and add the beef mince. Break it apart and then stir through the vegetables. Cook the beef for 4 minutes before adding the tomato paste and harissa. Stir thoroughly, season with salt and pepper, and then add the grated tomatoes. Mix well and cook covered on low heat for 15 minutes.
Fry Eggplants: Fry the aubergines in plenty of olive oil until golden on all sides. Then, remove them from the oil and place them on a wire rack to cool slightly.
Stuff Eggplants: Place the cooked aubergines into a large baking dish and use 2 spoons to open them up, ready to be filled. Fill each aubergine with 3-4 spoons of the beef mixture and top each one with a strip of bell pepper.
Prepare Sauce: In a small pot, add one tablespoon of olive oil and heat over medium-high. Once hot, add one tablespoon of tomato paste. Fry for 3 minutes before adding about 3/4 cup (approx. 200ml) of water. Mix well, then pour into the bottom of the baking dish with the aubergines.
Bake: Bake in a preheated oven at 180°C (350°F) for 25 minutes. Serve with some flatbread to soak up all the delicious flavours.