French Onion Soup with Cheese Croûtons from Life's Too Short to Stuff a Mushroom by Prue Leith

Ingredients

• 50 g/1¾ oz butter
• 2 garlic cloves, thinly sliced
• a pinch of salt, plus extra to season if needed
• 4 large onions, finely chopped (see hack)
• 2 tbsp olive oil
• 1.2 litres/40 fl oz/5 cups good beef stock (bouillon)
• 1 tsp caster (superfine) sugar
• 1 tbsp plain (all-purpose) flour
• 2-3 thyme sprigs, leaves picked
• 200 ml/7 fl oz/scant 1 cup white wine
• 1 bay leaf
• 100 g/3½ oz Gruyère, grated
• 50 g/1¾ oz Emmental, grated
• black pepper
• 4 thin slices of baguette, sliced at an angle
• 2 tbsp Dijon mustard