01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - Heat olive oil in a skillet over medium heat. Add diced potatoes and cook for 5-7 minutes until starting to soften. Add onion and bell pepper, cook for another 3 minutes. Stir in spinach and cook until wilted. Remove from heat and set aside.
03 - In the same skillet, cook diced bacon until crispy, about 5-6 minutes. Transfer to paper towels to drain excess fat.
04 - In a large bowl, whisk together eggs, milk, salt, black pepper, and smoked paprika until fully combined and smooth.
05 - Layer the sautéed vegetables, cooked bacon, bread cubes (if using), and half the shredded cheese in the prepared baking dish. Spread evenly.
06 - Pour the egg mixture evenly over the layered ingredients in the baking dish. Sprinkle remaining cheese on top.
07 - Bake for 35-40 minutes until eggs are fully set and the top is golden brown. A knife inserted in the center should come out clean.
08 - Let the casserole rest for 5 minutes before serving. Garnish with fresh chives or parsley and serve warm.