Heat a large skillet over medium-high heat, and add the butter to melt in. Add the sausage and onion cooking until the sausage is almost browned, about 3-4 minutes.
Add the garlic and potatoes and cook until the potatoes are browning and cooked through, about 10-15 minutes. You can pre-heat your oven at this point as well.
Add the spinach to the skillet and cook for one minute, and then turn the heat off. If you are prepping ahead, your hash is done at this point, and you can cool it, and store it away until you are ready to use it.
Put 1/2 cup of water in the bottom of a large casserole dish or roasting pan that has a lid. Place the bell pepper halves in the bottom of the pan, and fill each pepper with hash. Be sure to leave enough room for the egg! Crack an egg into each bell pepper, on top of the hash. Or, you can scramble the eggs and pour them into each cup if that is how your family prefers eggs!
Put the lid on your pan, and bake at 350 degrees for 25-30 minutes for sunny-side up eggs, or 30-40 minutes for scrambled. Check the peppers at the minimum times so you can be sure the eggs are set to your liking. You can take the lid off the pan for the last 10 minutes to melt cheese up top if you want too! Sea salt and pepper the tops as well as garnish with parsley if you wish.