2 large onions, thinly sliced
2 bay leaves
2 tsp plain (all-purpose) flour
500ml/17fl oz/2¼ cups hot vegetable stock
75ml/2½fl oz/5 tbsp dry white wine
salt and ground black pepper
For the cheese croûtes:
2 x 25g/1oz slices baguette
1 tsp Dijon mustard
2 tbsp grated reduced-fat Cheddar cheese
1 Lightly spray a large heavy-based pan with oil and place over a medium heat. Add the onions and bay leaves to the hot pan and cook very slowly for 15–20 minutes until the onions are really tender and starting to caramelize.
2 Stir in the flour and cook for 1 minute, then add the hot stock and wine. Increase the heat and bring to the boil. Season to taste with salt and pepper. Reduce the heat to a bare simmer and cook gently for 30 minutes.
3 Just before serving, preheat the grill (broiler). Toast the bread on one side only. Spread the untoasted sides with mustard and then sprinkle with grated Cheddar.
4 Divide the hot soup between two heatproof shallow bowls and float the croûtes, cheese-side up, on top. Pop the bowls under the grill for 2–3 minutes until the cheese melts. Serve immediately.