In a large, non-stick saute skillet over medium high heat, add olive oil and then place the chopped Swiss chard. Lightly sprinkle with salt and pepper and stir to coat with the oil. Cook until it wilts.
When the chard is cooked, put it on a big plate and set aside. Add more olive oil to the skillet and then the onions, sprinkling with a little salt and pepper. Let them cook and soften for about 10 minutes. You don't want these to caramelize--or maybe you do. When the onions are done, place them next to the chard on the plate and then cook the bacon.
When the bacon is done, place it on a few paper towels to soak up the grease and then add the cooked and chopped potatoes to the still heated pan with the bacon grease and stir well to coat. Sprinkle the potatoes with salt and pepper and let them cook over medium high heat so they crisp up nicely. While the potatoes are cooking, you can eat one piece of bacon and chop the rest. When the potatoes are ready, remove them and place on the plate with the chard and onions.
Turn the oven to 400 degrees.
In a big bowl, add the eggs and beat them well. Add two tablespoons or cream or milk and whip to combine. Sprinkle with salt and pepper.
In the same skillet you have been using, add enough butter to coat the bottom of the pan and place over medium heat. Pour in the eggs and gently scatter the mixed vegetables and bacon over the eggs to combine. Let the eggs cook slowly. When the bottom of the frittata is set--about 8 minutes--sprinkle the grated Parmesan on top and place the skillet in the oven to cook through.
When the frittata is done, flip on the broiler and let the top get golden brown. Remove from the oven and let cool thoroughly. Slice into quarters or eighths and lightly sprinkle with crunchy Maldon salt and more pepper. Serve as an appetizer or as an entree with salad and watch it disappear.