French onion soup recipe, with gruyère or comté croutons

Ingredients

• 100 g butter
• 1 kg onions (thinly sliced (see notes))
• 2 tbsp plain flour
• 200 ml white wine
• 100 ml dry sherry/port
• 1.5 litres beef stock
• Baguette (cut into 1-2cm slices.)
• 1 clove garlic
• 200 g gruyère or comté (grated)
• Cooking oil
• Salt
• Freshly-ground black pepper
• Method