1. Prep the Baking Dish:

• Spray a 9×13” baking dish generously with cooking spray.

2. Sauté the Leeks and Spinach:

• Heat olive oil in a medium skillet over medium-high heat.
• Add leeks and cook until they soften, about 5-7 minutes.
• Stir in the chopped spinach, cooking until it wilts. Remove skillet from heat.

3. Layer the Casserole:

• Place half of the bread cubes at the bottom of the baking dish.
• Layer with half of the diced ham, half of the leek/spinach mix, and half of the shredded cheese.
• Repeat the layers with the remaining bread, ham, leek/spinach, and cheese.

4. Prepare the Egg Mixture:

• In a medium-sized bowl, whisk together the eggs, milk, dijon mustard, salt, and pepper until well combined.
• Pour this mixture evenly over the layered ingredients in the baking dish.

5. Set to Marinate:

• Cover the baking dish with plastic wrap.
• Refrigerate overnight to allow the flavors to meld and bread to soak up the egg mixture.

6. Pre-Bake Steps:

• Remove the casserole from the refrigerator and let it sit at room temperature for at least 30 minutes.

7. Baking:

• Preheat your oven to 350°F.
• Remove the plastic wrap from the casserole.
• Bake in the preheated oven for 45-55 minutes. The top should turn a lovely golden brown, and the casserole should be cooked thoroughly.

8. Serving:

• Let it cool for a few minutes, then slice and serve.