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.
03 - Stir in onion and bell pepper. Cook for another 3 minutes. Add spinach and cook until wilted, about 1–2 minutes. Remove from heat and set aside.
04 - In the same skillet, cook diced bacon over medium-high heat until crisp, about 5–7 minutes. Transfer to paper towels to drain excess fat.
05 - In a large bowl, whisk together eggs, milk, salt, black pepper, and smoked paprika until fully combined and frothy.
06 - Layer the sautéed vegetables, cooked bacon, bread cubes (if using), and half the shredded cheese in the prepared baking dish.
07 - Pour the egg mixture evenly over the layered ingredients. Sprinkle the remaining cheese across the top.
08 - Bake for 35–40 minutes, or until the eggs are completely set and the top is golden brown. A knife inserted in the center should come out clean.
09 - Let the casserole cool for 5 minutes before serving. Garnish with freshly chopped chives or parsley and serve warm.