Wash, quarter the savoy cabbage, cut out and discard the core, and cut the savoy cabbage in 3 or 4 lengthwise cuts to get stripes.
Add water to the large pot, and add salt. Taste the water because it should be salty as you want the finished dish. Add more salt if necessary.
Peel and cut potatoes in the medium cubes, and add them to the pot with salted water.
Bring to a boil over high heat. Reduce to an active simmer and cook for 10 minutes.
After 10 minutes, add savoy cabbage, and continue cooking for next 10 to 15 more minutes or until the potatoes are fork tender and the savoy cabbage is soft.
Drain cooked potatoes and savoy cabbage, and return it to the pot. Add butter that is cut into pieces to the potatoes and gently mix it with a wooden spoon to combine. Optionally, you can add black pepper for extra flavor.
Instead of butter, you can use extra virgin olive oil. Use ½ tablespoon olive oil instead of butter.
Black pepper is optional, and if you prefer a slightly spicy flavor, then add it at the end. Instead of black pepper, you can add crushed red peppers.
If you like the flavor of the broth or stock, and you love cooking with it, then you can substitute part of the water or whole amount with broth or stock. Broths and stocks are ingredients where alliums may be hidden, so if you are using broth or stock make sure that is allium-free.