Margherita gnocchi bake

Ingredients

• 1 tbsp. olive oil 
• 1 onion, finely chopped 
• 2 garlic cloves, crushed 
• 1 tbsp. tomato puree 
• 1/4 tsp. chilli flakes (optional) 
• 200 g cherry tomatoes, halved 
• 1 400g can chopped tomatoes 
• 200 mL vegetable stock 
• 1 tsp. sugar 
• 1 tsp. balsamic vinegar 
• 20 g basil, roughly chopped 
• 500 g gnocchi
• 1 tbsp. mixed herbs 
• 125 g mozzarella, torn