Heat the oven to 200C. Halve and thinly slice the onions and coarsely grate the gruyere cheese.

In a medium, ovenproof deep saucepan, melt the butter over medium-high. Add the onions and season with salt and pepper. Cover and cook, stirring once or twice, until the onions are softened.

After 5 minutes, uncover the onions and strip the leaves from the thyme sprigs into the pot. add 1 tsp brown sugar at this point to help the onions caramelise. Cook until the onions are jammy and deep golden brown, roughly 10 to 15 minutes.

As browned bits appear, add a tablespoon or so of water and stir to combine. Once evaporated, add another tablespoon and repeat; this prevents burning and speeds the process up: (If you can caramelise the onions even longer, go for it: the darker their colour, the sweeter their flavour).

Next, add the vinegar and stir until evaporated. Remove from the heat, then add the beans with the veg or chicken stock. Season to taste and bring to a boil.

Reduce the heat slightly, then sprinkle the cheese evenly over top, especially around the edges for crispy bits. Bake in the oven until the cheese has melted and browned in spots for roughly 8-10 minutes. If the top is not as toasted as you’d like, bake for a minute or two.

Spoon into bowls and serve with the suggestions listed above.