For those unfamiliar with strata, it’s essentially a breakfast casserole reminiscent of a savory bread pudding or eggy stuffing. Built on a foundation of bread, eggs, and cheese, enhanced with milk and cream, and gussied up with an endless combination of add-ins—in this case, that includes crispy bacon and tender kale. All the work can be done the night before, so all that’s left is the simple task of putting it in the oven when you wake up.
The ideal strata should be creamy, not rubbery, and easy to slice into neat portions, with a slightly crisp top. Strata is composed of layers, just like the name suggests (‘strata’ is a geological term that refers to layers of rock or soil), which ensures that the ingredients are evenly dispersed, much like a lasagna.
In theory, you can use any type of bread: I tested with crusty baguette, sourdough, and even rye. None of these were particularly disappointing, but the clear winner was supermarket-style “French” or “Italian” bread. The finer hole structure, thin crust, and soft, pillowy texture improves the absorption and retention of the flavorful custard. Another great option is a quality white sandwich loaf, but I don't recommend brioche, which is a bit too rich given the other ingredients in the dish.
In order to create a custardy strata, the bread should really be one with the custard. A beautiful strata combiners the two ingredients completely, producing a fluffy, cloud-like texture. After some trial and error, I chose to measure by weight (not volume) and settled on the following ratio: 2 parts bread, 2 parts eggs, 2 parts dairy, 2 parts add-ins, and 1 part cheese. Keep in mind that a large egg generally weighs 2 ounces.
To ensure the bread absorbs the maximum amount of custard, it must be dried out. Drying the bread in the oven extracts moisture while leaving the crumb’s structure intact, making oven-dried bread a better option than stale bread, staling actually restructures the starch molecules, which can lead to unpleasantly chewy bread. Luckily, it's straightforward and doesn't take long to dry bread in a low oven.
I let the bread and custard soak in a large bowl for 30 minutes, stirring periodically to ensure the bread is well hydrated, before building the strata. I found that combining the two directly in a baking dish allows the custard to pool on the bottom, preventing some pieces of bread from being fully submerged, which produces an uneven texture in the final strata.
When baking a strata, please remember that not all bakeware is created equal and many brands are not broiler-safe—before proceeding, be sure to double check that your baking dish can withstand the heat of a broiler! I like the baking dishes by Emile Henry, which are both oven- and broiler-safe. If you use a dish that isn't broiler safe, like the ones. made by Pyrex, skip the broiling portion of the recipe (see note).
Strata is easily customizable, so feel free to try out your favorite add-ins or swap in different cheeses. Just keep in mind that high-moisture ingredients, such as mushrooms, spinach, or diced tomatoes, should be cooked or drained prior to assembly. Get creative and remember that beyond breakfast, strata also makes a wonderful lunch and dinner!
Adjust oven rack to middle position and preheat oven to 275°F (135°C). Spread bread in an even layer on a rimmed baking sheet, and bake until completely dried, about 35 minutes, rotating baking sheet and stirring bread cubes several times during baking. Remove from oven and allow to cool.
In a 12-inch cast iron skillet, cook bacon over medium heat, stirring frequently, until golden and crisp, about 10 minutes. Using a slotted spoon, transfer bacon to a paper towel-lined plate to drain. Drain and discard all but 1 tablespoon (15ml) bacon fat from the skillet. Add kale, season lightly with salt, and cook, stirring occasionally, until kale is wilted but still vibrant in color, about 3 minutes. Remove from heat and allow to cool.
In a large bowl, whisk together eggs, milk, heavy cream, Dijon, thyme, 3/4 teaspoon salt, pepper, and nutmeg until well combined. Add the dried bread and fold gently to combine. Let soak until bread is softened and slightly puffed, folding occasionally with a flexible spatula, at least 15 and no more than 30 minutes.
Grease an 8-inch square ceramic or anodized aluminum baking dish (see note) with butter. Using a slotted spoon, add half of the soaked bread to the prepared baking dish, spreading it in an even layer. Top with half of the kale, half of the bacon, and half of the Gruyère. Repeat with remaining bread, kale, bacon, and cheese. Pour any remaining custard over the layered strata. Using a flexible spatula, gently press down the top of the strata so that all the layers are submerged in the custard, but take care not to compress the bread. Cover tightly with aluminum foil. Allow strata to stand at room temperature for 30 minutes. Meanwhile, increase oven temperature to 325°F (160°C).
Bake strata until cheese is slightly melted, about 20 minutes. Remove foil, return baking dish to oven and continue to bake until strata is puffed and the center no longer jiggles when shaken, about 30 minutes. Remove from oven.
Adjust oven rack to 6 inches below broiler element and preheat broiler on high. Broil until surface of strata is lightly browned in spots, about 2 minutes. Transfer to heatproof surface and allow to cool for 10 minutes. Cut into portions and serve.
Special Equipment
Rimmed baking sheet, 8-inch square ceramic baking dish, slotted spoon, rubber spatula.
Notes
Before broiling the strata, please check that your baking dish is broiler-safe. Many baking dishes produced by popular brands, such as Pyrex, are not, so don’t take anything for granted and please refer to the manufacturer’s website for more information. Bear in mind that the timing may vary depending on the cookware involved, so pay close attention to the visual cues instead.
This recipe can be doubled and baked in a 9- by 13-inch baking dish.
Make Ahead and Storage
Bread cubes can be dried up to 4 days in advance. Spread dried bread on a sheet pan, cover loosely with aluminum foil, and store at room temperature.
The cooked bacon and kale can be refrigerated separately in airtight containers for up to 4 days.
After covering the uncooked strata with foil, it can be refrigerated overnight. When ready to bake, remove the strata from the refrigerator and let sit at room temperature for 1 hour; this will help the strata bake more evenly.
Leftovers can be stored in the baking dish covered with foil and refrigerated for up to 5 days. Reheat in the microwave in 45-second intervals.
To freeze, wrap individual portions tightly in plastic, transfer to a resealable freezer bag, and store in the freezer for up to 3 months. Allow to thaw in the refrigerator overnight before reheating.