Healthy meatball bake

Ingredients

• 2 tbsp olive oil
• 1 red onion, roughly chopped
• 1 g sweet potatoes, peeled, cut into chunks
• 2 garlic cloves, crushed
• 400 g can chopped tomatoes
• 2 tbsp tomato purée
• 1 tsp oregano
• 1 bay leaves
• 1/5 tsp black pepper
• 1 bread loaf, 1 slice, crust removed
• 5 ml whole milk, 4 tbsp
• 1 red onion, finely grated
• 1 carrot, peeled
• 1 courgette, trimmed, finely grated
• 500 g lean minced beef
• 1 eggs, yolk only
• 100 g mozzarella, grated
• 1 tsp black pepper