Lyonnaise onions: in a wide-based pan over medium heat, sweat the sliced onions with the salt until soft. Add the butter and cook for another hour or so, until very soft and golden brown. Stir in the sherry vinegar, then remove from the heat and reserve.
Slice the Charlotte potatoes to approximately 5mm thick.
Restack each potato in its original order, discarding the end pieces.
Spread the Lyonnaise onions evenly over the base of a cast iron pan.
Arrange the potato stacks around the edge of the pan on top of the onions and tuck in the bay leaves.
Season only the potatoes generously with Maldon sea salt.
Dot the potatoes with diced butter.
Pour in enough chicken stock to cover.
Bake at 180°C fan (about 350°F fan) for approximately 40 minutes.
Check every 10 minutes, reducing the temperature if the potatoes colour too quickly.
Top up with additional chicken stock if required during cooking.
Cook until the potatoes are tender and the stock has reduced around them.
Michelin-style boulangère from chef Adam Byatt: crispy top, soft centre, with sweet caramelised Lyonnaise onions. Using a good brown chicken stock makes all the difference. Via Instagram (@adambyatt).
