Made with buttery brioche, salty bacon, and mild sweet leeks, this savory bread pudding is a versatile dish that's a cinch to prepare and loaded with flavor.
Preheat the oven to 350°F and butter a baking dish (see notes on size).
Leaving the crust on, cut the bread into 3/4-inch cubes, place them in a large mixing bowl, and set aside.
Fry the bacon in a large pan over medium heat until cooked through, but not too crispy. Transfer to a paper-towel-lined plate and pour off all but a couple of teaspoons of the fat from the pan.
Melt 1 tablespoon of the butter with the remaining bacon fat over medium heat and add the garlic. Sauté until fragrant, about 1 minute, then add the leeks and cook until soft and tender, 4 to 5 minutes.
Return the bacon to the pan, add the thyme, sprinkle with the salt and few grinds of black pepper. Taste and adjust the seasoning if needed, then transfer the mixture to the bowl with the bread cubes and combine.
Cut the remaining 3 tablespoons of butter into small pieces and add to a microwave-safe bowl. Heat for 10 seconds on high, stir and continue microwaving in 5-second increments until fully melted.
Whisk the milk into the melted butter, then whisk in the eggs. Slowly pour the mixture over the bread cubes and leeks while tossing gently until the bread is evenly coated.
Spread the mixture in the prepared baking dish and set aside for 20 minutes to let the bread absorb the custard.
When ready to bake, set the baking dish inside a larger, deeper pan. Pour enough boiling water into the outer pan to come about halfway up the sides of the dish with the pudding (see notes about using a bain-marie). Carefully transfer the dishes to the oven.
Bake for 50 to 60 minutes or until the pudding is set and a butter knife inserted in the center comes out clean.
Remove the pudding from the oven, remove it from the bain-marie, cover the baking dish with aluminum foil and keep warm until ready to serve.
Notes
ABOUT THE BAKING DISH
We recommend using a medium-size baking dish (around 2 qt) so the bread pudding fills it up, almost to the top. If you spread it out too much in a larger casserole (i.e. 13×9-inch), it may dry out. For a moist, fluffy texture, a smaller dish is best.
HOW TO CLEAN LEEKS
Leeks can trap sand between their layers of leaves, so you'll need to wash them carefully. Here's how:
Trim off roots and the upper, dark green portion of the leaves (this is generally too tough to eat) and discard. You'll be using the bottom white part and some of the light green.
Slice the leeks in half lengthwise, then crosswise into 1/4-inch slices
Place them in a salad spinner, fill the bowl with water, swish them around a little, then leave them to float for about 10 minutes. The sand should filter out and sink to the bottom of the bowl. Lift the colander out, rinse the bowl, then repeat the process, but without the soaking time. Spin dry as you would any salad greens.
How to Make and Use A Bain Marie
A bain-marie (French for water bath) is a simple technique that surrounds custard-based dishes like this one with hot water during baking to produce an even, gentle heat. Here's how to use it:
Select an outer container that is deep enough to hold water reaching about 1/2 to 2/3 of the way up the sides of your baking dish. The container should also be large enough to leave at least 1 inch of space between the inner dish and the outer container.
If desired, you can line the bottom of the outer container with a kitchen towel to keep the inner dish from sliding around inside the pan.
Position what you're baking in the bain-marie container and slowly pour boiling water into it. Add enough to reach halfway up the side of your inner baking dish.
Very carefully, move the dishes to the oven and bake your recipe according to the instructions.
Remove your food from the bain-marie as soon as it’s done, because if left in the hot water, it will continue to cook, even once it’s out of the oven.