How to Make It
Place potatoes, garlic, and salt in a large saucepan; add water to cover potatoes by 2 inches. Bring to a boil over high. Reduce heat to medium-low; simmer until very tender, about 22 minutes. Drain; return potatoes and garlic to pan.
Cook potato mixture over low, stirring constantly, until all water has evaporated, about 3 minutes. Mash using a potato masher. Add buttermilk, sour cream, and butter; mash until potatoes are mostly smooth. Remove from heat.
Stir in pepper and 2 tablespoons each of the chives, parsley, and dill. Season with salt. Transfer to a serving dish; sprinkle with remaining 1 tablespoon each chives, parsley, and dill