Gnocchi, aubergine and tomato bake recipe

Ingredients

• 1 onion, sliced
• 1 medium-large aubergine (eggplant), cut into bite-size chunks
• 3 tbsp olive oil, plus extra for drizzling
• 1 x 400g/14oz tin chopped tomatoes
• 1 tbsp tomato purée
• 1 clove garlic, grated or crushed
• 1 tsp caster (superfine) sugar
• 1 tsp balsamic vinegar
• 1 handful chopped basil
• 450 g fresh gnocchi
• 200 g mozzarella
• 1 pinch each of flaked sea salt and freshly ground black pepper