Adapted from Thomas Keller
2 cups 1/2-inch-thick slices leeks (white and light green parts only)
4 tablespoons (2 ounces) unsalted butter
Freshly ground black pepper
12 cups 1-inch cubes crustless Brioche or Pullman sandwich loaf
1 tablespoon finely chopped chives
1 teaspoon thyme leaves
3 large eggs
3 cups whole milk
3 cups heavy cream
Freshly grated nutmeg
1 cup shredded Gruyere
Preheat the oven to 350F.
Put the leek rounds in a large bowl of tepid water and swish so that any dirt falls to the
bottom of the bowl. Set a medium saut pan over medium-high heat, lift the leeks from
the water, drain, and add them to the pan. Season with salt and cook, stirring often, for
about 5 minutes. As the leeks begin to soften, lower the heat to medium-low. The leeks
will release liquid. Stir in the butter to emulsify, and season with pepper to taste. Cover
the pan with a parchment lid, and cook, stirring every 10 minutes, until the leeks are
very soft, 30 to 35 minutes. If at any point the butter breaks or looks oily, stir in about a
tablespoon of water to re-emulsify the sauce. Remove and discard the parchment lid.
Meanwhile, spread the bread cubes on a baking sheet and toast in the oven for about
20 minutes, rotating the pan about halfway through, until dry and pale gold. Transfer to
a large bowl. Leave the oven on.
Add the leeks to the bread and toss well, then add the chives and thyme.
Lightly whisk the eggs in another large bowl. Whisk in the milk, cream, a generous pinch
of salt, pepper to taste, and a pinch of nutmeg.
Sprinkle 1/4 cup of the cheese in the bottom of a 9-by-13-inch baking pan. Spread half
the leeks and croutons in the pan and sprinkle with another 1/4 cup cheese. Scatter the
remaining leeks and croutons over and top with another 1/4 cup cheese. Pour in
enough of the custard mixture to cover the bread and press gently on the bread so it
soaks in the milk. Let soak for about 15 minutes.
Add the remaining custard, allowing some of the soaked cubes of bread to protrude.
Sprinkle the remaining 1/4 cup cheese on top and sprinkle with salt.
Bake for 1 1/2 hours, or until the pudding feels set and the top is brown and bubbling.