I really do love a good bowl of French onion soup. This is best made with a fresh stock from the butchers but a supermarket one (not from concentrate) will do just fine, too.
Preheat the oven to 150C/300F/Gas 2.
Place a large pan on a medium heat with a drizzle of oil and the butter. Add the onions to the pan with the bay leaf, pop a lid on and leave to cook for about 25 minutes until soft. Give them a good stir every now and then so they don’t burn. If they look like they are catching at anytime, just add a little more oil.
Trim the baguette ends, cut it into eight slices (about 2cm/1in thick) and lay them on a baking sheet.
Next, roughly grate the Gruyère (or parmesan) into a bowl, sprinkle the mustard powder over (if using) and toss it all about to mix together. Then divide it evenly between the tops of the bread slices.
Once the onions are a few minutes off being ready, place the croûtons into the oven to bake for about 4-5 minutes. You could also grill them for about five minutes if you prefer.
Once the onions look lovely and soft, add the garlic, sage and flour, giving them a good stir in. Cook for 2-3 minutes to remove any floury taste. Pour in the beef stock, put the lid back on, increase the heat and bring the soup up the boil. Then leave it to bubble away for about 2-3 minutes before removing it from the heat. Season, to taste, with salt and pepper.
Remove the cheese-topped, crisp croûtons from the oven. Pick and roughly chop the parsley leaves.
Divide the soup among four wide serving bowls and serve with the croûtons either sitting right on top of the soup or to the side. Scatter the parsley over and serve.
Type the ingredients you want to use, then click Go. For better results you can use quotation marks around phrases (e.g. "chicken breast"). Alternatively you can search by chef, programme, cuisine, diet, or dish (e.g. Lasagne).