The Secret Ingredient for Incredible Mashed Potatoes

Name: The Secret Ingredient for Incredible Mashed Potatoes
Ingredients: 2 1/2 pounds russet potatoes , peeled and cut into 2-inch pieces; 3 tablespoons plus 1 1/2 teaspoons kosher salt , divided; 1 cup heavy whipping cream or half and half; 6 tablespoons unsalted butter , divided; 1 (5.2-ounce) package garlic and herb gournay cheese (such as Boursin Garlic and Fine Herbs), at room temperature; 1/4 teaspoon freshly ground black pepper; Finely chopped mixed tender fresh herbs (such as chives and flat-leaf parsley), optional