Peel and thoroughly rinse the russet potatoes. Cut them into evenly sized 1–2-inch chunks or quarters so they cook at a consistent rate, then transfer them to a large cooking pot.
Pour approximately 6–8 cups of chicken broth over the potatoes, using enough broth to completely cover them.
Set the pot over high heat and bring the broth and potatoes to a full boil. Once boiling, lower the heat to medium and allow the potatoes to simmer for approximately 15 minutes, or until they are tender enough to be pierced easily with a fork.
While the potatoes cook, place the salted butter and softened cream cheese into a large mixing bowl. Allowing these ingredients to soften further will help them blend evenly into the hot potatoes.
When the potatoes are fully tender, drain away most of the chicken broth while retaining a small amount of liquid in the pot.
Carefully transfer the hot potatoes and the reserved broth into the mixing bowl containing the butter and cream cheese. Add the buttermilk and 1 teaspoon of salt.
Using a potato masher or hand mixer, mash and blend the mixture until the potatoes become creamy, light, and fluffy, with no noticeable lumps remaining.
Taste the mashed potatoes and add additional salt only if needed.
Serve immediately while hot alongside the main dish of your choice.