Place the potatoes in large pot or Dutch oven. Add the chicken broth and enough water to cover them by about 1- to 2-inches. Place over HIGH heat and bring to a boil. Reduce heat, cover, and simmer for 20 to 25 minutes, or until very tender all the way through when pierced with a fork or the tip of a sharp knife. Drain well.
Meanwhile, warm the buttermilk in a saucepan over LOW heat or in the microwave at half power for 10 second intervals, just until warm. Don't let it boil or it will separate and curdle. Set it aside.
Return the well-drained potatoes to the warm, empty pot and set it over LOW heat. Heat, tossing the potatoes, for a minute or two to evaporate any remaining moisture and let the potatoes dry a bit. Remove them from the heat.
Use an electric hand mixer on LOW speed to break up the potatoes a little then add the butter, about half of the warmed buttermilk, and the salt. Beat again on MEDIUM speed, adding the remaining buttermilk as you mix. Mix just until creamy and smooth. Avoid overworking the potatoes as it can result in a gummy, gluey texture. Taste and add additional salt, if needed.
Serve as is or garnish with chives and freshly ground black pepper, if desired.