Ultimate Breakfast Casserole

Directions

• Before We Start

  Bread matters: Homemade sourdough is ideal—it soaks up custard without turning into mush. It’s also great if your bread is 1-3 days old. Our “4 thick slices” is a good visual target. If you’re using thinner, pre-sliced sandwich-style sourdough, go by weight instead—you’ll likely need 5–6 slices to hit the same amount.
  Cheddar buying: When we say “aged extra sharp” we mean it look for 12 months aged cheddar or 9-10 months if you can’t find it.. The flavor is sharper, nuttier, and it actually shows up in a rich egg base. If you want a brand rec when you can find it: Croc is fantastic.

• Caramelize the Onions (Slow, Buttery, Worth It)

  In the same skillet, keep the rendered fat. Add the onion, 1.5 Tbsp (22 g) butter, and 1/2 tsp Morton kosher salt.
  
  Cook over medium-high heat until the onions start to sweat and pick up light browning.
  
  Add about 1/4 cup (60 g) of water. and scrape up the browned bits. From here, keep cooking 35–45 minutes, adding a 1/4 cup (60 g) water from the reserved water whenever the pan dries out (you’ll add water 3–4 times total).
  
  You’re done when the onions are deep brown and sweet, not just “kinda soft.”

• Brown the Sausage (Crispy Edges on Purpose)

  In a large skillet over medium-high heat, cook the sausage, breaking it up as it cooks.
  
  Once it’s mostly cooked through and has turned that light brown/gray-ish color, spread it out in an even layer, crank the heat to high, and let it go untouched for 2–3 minutes to build a crispy crust on one side.
  
  Add the thyme, stir, then set aside off the heat.

• Cube the Bread

  Cut the sourdough into 1/2-inch cubes and spread it in the baking dish.
  
  Crust/heels are optional. If you like a little chew, trim off the hard crusty bottom/heels and slice those bits thin—chewy is good, a jaw workout is not. If you want a softer casserole, just discard the super-hard pieces. We typically leave out the bottom crust but keep the rest.

• Make the Custard

  In a large bowl, whisk together the heavy cream, milk, eggs, and 2 1/2 tsp kosher salt (from the divided salt).

• Assemble

  Scatter the sausage and caramelized onions over the bread. Sprinkle on the cheddar.
  
  Pour the custard evenly over the top.

• Rest

  Just like a great french toast, letting this casserole rest in the fridge for 2 hours (preferably overnight) will give the bread time to soak up all that custard giving it an irresistible texture. If you are making it the morning of, it is perfectly fine to go straight to baking, but making it the night before is the way to go!
  
  Personal Note: This is our recipe for Christmas morning breakfast, we make it a day in advance then pop this in the oven. Makes for a gourmet breakfast without a lot of time and energy on Christmas day.

• Bake

  Take it out of the fridge and crack black pepper on top. Bake at 350°F (175°C) for 45–55 minutes (ours was done at 50 minutes), until the center is set (it shouldn’t slosh) and the top is browned.
  
  Let rest 10 minutes before slicing—this finishes setting and makes cleaner pieces.