Cheesy Garlic Duchess Potatoes

Name: Cheesy Garlic Duchess Potatoes
Prep time: 20 min
Cook time: 32 min
Total time: 52 min
Cuisine: European, French
Ingredients: 2 1/2 pounds medium Yukon Gold potatoes; 1 tablespoon plus 3/4 teaspoon kosher salt, divided; 2 ounces Gruyère cheese, finely grated (about 1/2 cup); 3 cloves garlic; 6 tablespoons unsalted butter, divided; 3 tablespoons whole milk, heavy cream, or half-and-half; 3/4 teaspoon freshly ground black pepper; 4 large egg yolks; 1 tablespoon finely chopped fresh chives