Peel and cut the potatoes into chunks. Divide the butter into 4 tablespoons, 2 tablespoons and 2 tablespoons for use in mashing, cooking the cabbage and serving.
Cook and mash the potatoes
In a large pot, add the potatoes and enough water to cover them by about an inch.
Bring to a boil, then reduce to a steady simmer, and cook until tender (about 15 minutes).
Drain the potatoes in a large colander and let them sit 5 minutes.
Add the potatoes back into the pot, add the milk, 4 Tbs butter, salt and pepper and mash until smooth.
Cook the bacon and cabbage
In a skillet, cook the bacon until crispy. Remove and drain on paper towels.
In the same skillet, add 2 tablespoons butter and cook the cabbage until soft and wilted.
Assembly
Combine the mashed potatoes, cooked cabbage, and bacon together.
Stir the scallions through.
Test for seasoning and add salt/pepper if desired.