Step 1

Bring a large saucepan of salted water to a boil, add the potatoes, and cook until tender, 20 to 30 minutes. Drain and let cool slightly.

Step 2

Preheat the oven to 430°F (220°C).

Step 3

Let the potatoes cool for about 10 minutes and then lightly smash them with your fist or the bottom of a heavy skillet.

Step 4

Place them in an ovenproof dish with the garlic and bay leaf, drizzle with 2 tablespoons oil, and gently turn to ensure they’re thoroughly coated. Season with salt and white pepper and bake until golden brown and crisp, 25 to 30 minutes.

Step 5

Meanwhile, in a skillet over low heat, warm 1 tablespoon oil and then add the onions and season with salt and white pepper. Cook gently until very soft and translucent, about 20 minutes.* Try squeezing a piece of onion; it should be very soft and taste sweet.

Step 6

Increase the heat and let the onions caramelize and turn golden brown, stirring to stop them from sticking, about 5 minutes more. Remove the cartouche, if using, and set aside. Add a splash of sherry vinegar for a little bit of acidity that cuts through the cheese.

Step 7

Take the potatoes out of the oven and scatter the onions and spoon or scatter the cheese on top. Return the dish to the oven and cook until golden brown and bubbling, 5 to 10 minutes.

Step 8

Remove from the oven and serve right away, sprinkled with a little cracked black pepper.