British onion soup with Welsh rarebit toasts | British Onions

Ingredients

• 1 tablespoon olive oil
• 2 tablespoons butter
• 1 kg British onions, finely sliced
• A few sprigs of thyme
• 2 bay leaves
• 300ml dark ale
• 1 litre beef stock, fresh if you can get it
• 100g mature cheddar
• ½ teaspoon British mustard
• ½ egg yolk
• A couple of dashes of Worcestershire sauce
• 1 tablespoon dark ale
• Salt and pepper
• 8 slices if sourdough or white baguette