Rosemary Gruyere Popovers

1 tablespoon unsalted butter, plus more for pan
3 large eggs
1 cup milk
1 cup flour
1/2 teaspoon salt
3/4 cup grated gruyere cheese
2 tablespoons rosemary, finely chopped

Heat oven to 450. Grease popover pan with butter and set aside. Melt 1 tablespoon butter in a small saucepan. Remove from heat and set aside to cool. Stir in eggs and milk. Mix together flour and salt and then whisk in egg mixture - working slowly so to avoid lumps. Fold in cheese and rosemary. Divide batter between prepared popover cups and place in the oven. Bake for 15 minutes. Reduce heat to 350 and bake an additional 20 minutes. Remove from oven and serve immediately with whatever other food you happen to still have in the house - a crisp green salad is nice.