Place potatoes in a large pot and cover them completely with water.
Cover the pot and bring to a boil. Add salt to pot and boil potatoes, uncovered, until they're fork tender, about 20-25 minutes.
Drain potatoes and return them to the pot.
Add butter, milk, and cheese to the potatoes and mash until incorporated.
Season to taste with salt and pepper.
Using a pastry bag, pipe mashed potatoes into 8 oz. mason jars. Alternatively, you could scoop potatoes into jars.
Top mashed potatoes with sour cream, chives, crumbled bacon, and additional cheese.