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. Sauté diced potatoes 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 bacon until crisp and browned. Transfer to paper towels to drain excess grease.
04 - Whisk eggs, milk, salt, pepper, and smoked paprika in a large bowl until fully combined and frothy.
05 - Layer sautéed vegetables, crispy bacon, bread cubes (if using), and half the shredded cheese in the prepared baking dish.
06 - Pour the egg mixture evenly over the layered ingredients. Sprinkle remaining cheese across the top.
07 - Bake for 35–40 minutes until eggs are completely set and the top is golden brown. A knife inserted in the center should come out clean.
08 - Let casserole rest for 5 minutes before serving. Garnish with fresh chives or parsley and serve warm.