Get a large wide saucepan over a medium heat with the butter.
Peel and slice the onions as finely as possible
Add to the hot pan along with a large pinch of salt and pepper and the bay leaf
Stir well and cook over a high heat for 5 minutes until the onions start to release some juices
Turn the heat down to low, cover and allow to cook for 10 minutes, stirring occasionally
Once the onions have released their juices and started to colour remove the lid and continue cooking very gently for 1 hour, stirring occasionally until deep golden brown
Tip in the flour and stir to combine
Finely chop the thyme and add that along with the brandy
Turn the heat back up to high and cook until the brandy has reduced by half
Repeat with the white wine and then add the beef stock
Simmer for 1 hour over a low heat
Taste and adjust the seasoning, allow the soup to cool and then refrigerate overnight
For the Watercress salad:
Finely chop the cornichons and add to a large serving bowl.
Tip in the mustard, olive oil and cider vinegar
Season with salt and pepper and then mix well with a fork
Add the watercress and toss together
Serve alongside the bubbling gratinated soups
For the Croutes:
Preheat drawer 1 of the Air fryer to Bake at 320°F and drawer 2 to Reheat at 285°F for 6 minutes.
Cut 2x 2cm thick slices from the baguette.
Fill 2 ramekins with the chilled soup.
Once preheated, toast the baguette slices and reheat the soup in the ramekins at the same time
Remove the toasted bread slices from the Air fryer and lay one slice of toast on top of each soup ramekin
Generously grate over the gruyere cheese
Replace the drawer into the Air fryer, set Air fryer to Grill at 390°F for 3 minutes or until the cheese is golden and bubbling