Steep the cream. Combine 1 ¼ cups heavy cream, 1 ¼ cups whole milk, 2 sticks of unsalted butter, 3 cloves smashed garlic, and fresh herbs (any combination of thyme, sage, and rosemary) in a medium saucepan. Bring to a simmer, just until the butter has melted. Turn off the heat, then let the liquid infuse and steep for 15 minutes.
Cook the potatoes. Place the peeled, cubed potatoes in a large pot, then cover with water and bring to a rapid boil. Add a teaspoon of Kosher salt, then cook until tender, about 20 minutes. Drain the potatoes, return to the hot pan for 5 minutes, just to help evaporate any excess liquid. Working in batches, pass the potatoes through a foley mill (fitted with attachment with the smallest holes) or a ricer into a large mixing bowl.
Strain the cream. Strain the infused cream mixture right into the bowl of riced potatoes. Season with 2 tsp of Kosher salt and a ¼ tsp freshly ground black pepper, then stir until thoroughly mixed. Taste and adjust seasoning, as needed.
Broil the potatoes. Heat the broiler and position a rack directly underneath it. Transfer the potatoes into a large baking dish (the size doesn't really matter, just something large enough to hold them all). Use a spoon or spatula to swirl the top however you like. Broil for about 10-12 minutes, checking the potatoes every few minutes to ensure they brown evenly and rotating the pan as needed. Serve immediately!