Horseradish Mashed Potatoes

Ingredients (7)

• 2 1/2 pounds russet potatoes, or Yukon gold, peeled and cut into 1-inch cubes
• 1 teaspoon salt, plus more for seasoning
• 6 tablespoons butter
• 2 tablespoons horseradish, finely grated
• 1 cup whole milk, or 2 percent
• 1/2 cup plain full-fat Greek yogurt, or 2 percent
• Chopped parsley, optional, for garnish