Gruyere Chive Popovers

Preheat oven to 400 ºF. In a medium saucepan over medium heat, warm the milk just until bubbles form around the edges. Sift the flour and salt together in a bowl. Set aside. In a separate large bowl, whisk the eggs until frothy, and then slowly whisk the warm milk into the eggs, whisking constantly so eggs don't cook. Whisk in the flour mixture just until combined, then whisk in 1 cup of the cheese and the chives. Place the popover pan in the oven for 2 minutes to heat. Remove it and add a pat of butter to each cup. Once the butter has melted, portion the batter into the cups, filling each about 3/4 full. Top with a portion of the remaining cheese. Bake the popovers for 20 minutes, then reduce the oven temperature to 300 ºF, and continue baking about 10 more minutes. (See Kelly's Notes.) Remove the popovers from the oven and serve warm.