Ingredients

• 6 medium onions, thickly sliced
• 4 garlic cloves, roughly chopped
• 2 tbsp balsamic vinegar
• 2 tbsp caster sugar
• Small bunch fresh thyme
• 100g unsalted butter
• 1 litre fresh beef stock
• 300ml fino sherry
• 1 baguette or sourdough loaf
• 200g gruyere cheese

Method

1. Heat the oven to 140C.
2. Divide the onions and garlic equally between 2 medium roasting tins.
3. Add 1 tbsp vinegar, 1 tbsp sugar, half the thyme, and 50g butter to each tin. Divide the stock and sherry equally between the tins.
4. Cover both tins with a layer of baking paper then a layer of foil. Transfer to the oven and cook for 2.5 hours.
5. Optional: transfer the contents of the tins to a heatporoof ceramic 2 litre dish. Set the grill to high. Place the bread slices on top of the onion soup then top with cheese. Put under a hot grill for 5 minutes or until the cheese has melted and turned golden. Serve straightaway.