Preheat oven to 350 degrees F.
Grease 9x13" baking dish.
Cut bacon into bite-sized pieces.
In a large skillet over medium-high heat, cook bacon.
Once cooked, remove from pan and set aside.
In the same skillet wipe out most of the excess bacon grease, and add olive oil over medium heat.
Add leeks, season with salt, and cook until softened, about 10 minutes.
Combine cooked bacon, leeks, and bread, tossing to combine.
Place in baking dish.
Whisk together eggs, milk, and salt. Pour over bread mixture.
Top with cheese. At this point you can either bake it immediately, or refrigerate 2 hours or up to overnight.
Bake in preheated oven for 55-60 minutes. If you refrigerated it overnight, you will likely need to add 10 minutes to the baking time. If the cheese starts to get too brown, cover with aluminum foil.
Serve and enjoy!