ULTRA-CREAMY MASHED POTATOES

Steps:

• Place potatoes in a large pot and pour in cold water to cover by 1". Add a large handful of salt (water should taste briny, like the ocean) and bring to a boil. Reduce heat and simmer until potatoes are very tender but not crumbly, 30-35 minutes. Drain, briefly rinse with cool water to remove any excess starch, and return potatoes to warm pot (off heat) to dry while you heat the milk mixture.
• Warm milk, cream, garlic, and rosemary sprigs in a small saucepan over medium until fragrant, about 5 minutes. Remove pan from heat.
• Pass hot potatoes through ricer or food mill into a large bowl (cold potatoes will become gummy). Add butter and 4 tsp. salt and stir until butter is completely incorporated. Strain warm milk mixture through a fine-mesh sieve into a large measuring glass. Pour into potatoes 1/2-cupful at a time, stirring after each addition until liquid is fully incorporated and mixture is smooth before adding more.
• Serve mashed potatoes topped with a few grinds of pepper.
• Do Ahead
• Mashed potatoes can be made 1 day ahead. Cover and chill. Reheat over medium, stirring often and adding 1/4 cup milk or stock to thin out if needed.