Preheat an oven or toaster oven to 400 F. Bring a medium pot of water to a boil. Wash and remove stems from greens. Large dice your onion and protein.

Peel and cube your potato. Boil for 12-14 minutes (until tender but not mash-able). Drain and set aside.

In a small, oven-safe pan, heat butter or oil over low/medium heat. Swirl the pan or use a spray so sides are also coated. Add in onion and cook while stirring for 1-2 minutes, until translucent. Stir in protein.

Add your greens to the pan to wilt (here is where I usually panic that I've tried to add too many greens and have to reassure myself that they WILL cook down). Add salt and pepper to your own taste. Pop a lid over your pan to speed the wilt up, but it should only take a minute or two.

Meanwhile, crack and whisk your eggs together. You want enough volume to fill the pan to a depth of about an inch (5 eggs in my 8 inch pan with this amount of other ingredients). Mix the ingredients in your pan until they're evenly distributed, then add the eggs in. Turn heat up to medium.

Let cook for 3-4 minutes. You may need to add time depending on size. You're done this step when the edges of the frittata are cooked enough that you can pull them away from the pan with a spatula - but most of the top is still raw/liquid.

Sprinkle your cheese over top of the frittata and then pop it into the oven. Bake for about 10 minutes (again - adjust for the size of your pan). Signs that your frittata is done include no jiggle if you shake the pan and starting to brown on the top. Remove from oven and let sit for 2 minutes.

Slice, serve and enjoy! I always forget that the pan handle will be hot, so I recommend putting an oven mitt over the handle for safety. And don't panic if you cut into it and find your frittata underdone - pop it back into the oven for 2 minutes at a time until fully cooked.