Place the half-and-half in a medium saucepan along with the garlic cloves, thyme, rosemary, and chive stems. Bring the half-and-half to a simmer, then turn down until it is barely simmering and is reduced by 1/2 cup, about 8-10 minutes.
Strain the half-and-half through a sieve, discarding the herbs and garlic. Set the warm half-and-half aside.
Peel the potatoes and dice them into 2-inch pieces. Place the diced potatoes in a pot of cold water with a tablespoon of salt. Bring the potatoes to a boil over high heat, then reduce to a simmer and cook until the potatoes can gently be pierced with a fork, about 15 minutes.
Drain the potatoes in a colander, shaking off any excess water, then place them back in the pan over low heat. Cook, stirring constantly, to dry out the bottom of the pan for a minute, then place the potatoes in a large bowl. (If you’d like, you can wash the pot and dry it and rice the potatoes back into this pot.)
Rice the potatoes in batches into the pot. Alternatively, mash the potatoes in the pot until most of the lumps are gone. (Note: Do not place the potatoes in a food processor or stand mixer to puree. They will become gluey and sticky.)
Once all of the potatoes are mashed, pour in the cream and a tablespoon of salt and stir gently. Add the butter and stir until melted. Taste, adding more seasoning or butter if desired.
Serve immediately, or cover and allow to cool, then refrigerate overnight. To reheat, place the potatoes over very low heat on the cooktop and add 2 tablespoons of half-and-half and 2 tablespoons of butter. As they begin to reheat, slowly stir them to incorporate the other ingredients, being careful not to overwork them.