First, preheat the oven to 350°F.
Prepare all ingredients prior to cooking for a seamless process. Dice your onion and bell pepper. Chop your spinach. Then, using a vegetable peeler, remove the skin and any blemishes from the sweet potato and grate it. Be careful of your fingers during this process!
Next, using kitchen shears, cut bacon into small strips, about ¼" thick. Place directly into a cooking pan. Then, heat pan to medium-heat and cover with a lid. Again, be careful of the bacon grease here. It will get everywhere. (That's why we have the lid.) If you have a splatter guard, that would be great to use here as well.
Cook the bacon for 6-8 minutes or until 90% cooked. Then, drain grease from the pan. Pro Tip: Save a tablespoon or two of the grease to drizzle on top of the casserole. IT'S SO GOOD.
Keep the bacon in the pan over medium-heat. Then, add in sweet potato, onion, and bell pepper. Sprinkle in 2 tablespoons of breakfast blend seasoning and sauté vegetables until golden. (Don't cook them completely through.) Set aside.
In a mixing bowl, whisk together eggs, egg whites, milk, and 2 more tablespoons of breakfast blend seasoning and pour into a greased baking dish.
Add bacon and vegetables into the egg mixture. Then, stir in chopped spinach.
Lastly, sprinkle shredded cheese on top.
Bake for 40 minutes. At the 30 minute mark, cover the casserole dish with tin foil to prevent the cheese from burning.
Remove from the oven and garnish with avocado slices and green onion. Slice into squares, and enjoy!