- 3 pounds russet potatoes, peeled, cut into 1-inch cubes
- 2 cups crumbled creamy blue cheese (such as Bleu d'Auvergne; about 8 ounces)
- 1/2 cup (or more) whole milk
- 2 1/2 teaspoons chopped fresh rosemary
- Fresh rosemary sprigs (optional)
Cook potatoes in large pot of boiling salted water until very tender, about 15 minutes. Drain well. Return potatoes to pot. Add cheese and 1/2 cup milk and mash until almost smooth, adding more milk by tablespoonfuls for desired consistency. Stir in chopped rosemary. Season to taste with salt and pepper. DO AHEAD Can be made 8 hours ahead; cover and chill. Rewarm covered with plastic wrap in microwave, stirring occasionally and adding more milk, if desired.
Transfer mashed potatoes to bowl. Garnish with rosemary sprigs, if desired.