Peel and cut the Yukon Gold potatoes into 1-inch cubes. Place in a pot, cover with cold water, and add 1 tablespoon of kosher salt. Boil, then reduce to a simmer for 15-20 minutes until fork-tender; drain well.

In a medium saucepan, combine heavy cream and butter over medium heat, stirring until the butter melts. Add garlic cloves and rosemary, steep on low heat for 10 minutes, then remove solids.

Return drained potatoes to the pot over low heat to evaporate moisture. Mash the potatoes until smooth, avoiding over-mashing.

Gradually pour the warm cream mixture into the potatoes, stirring until smooth. Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper.

Spoon into a serving dish and garnish with extra rosemary and a pat of butter.