How to Make It
Preheat the oven to 400°F. Butter a 6-cup gratin dish and set it aside. Melt the 3/4 stick of butter in a saucepan, then add the flour and mix it in well with a whisk. Cook for 10 seconds, add the cold milk in one stroke and mix it in with a whisk. Keep stirring with the whisk until the mixture thickens and comes to a strong boil, about 2 minutes. It should be thick and smooth. Remove from the heat, and stir in the salt and pepper.
Break the eggs into a bowl and beat well with a fork. After about 10 minutes the white sauce should be cool enough to proceed. Add the eggs, cheese and the chives to the sauce, and mix well to combine. Pour into the buttered gratin dish and cook immediately, or set-aside until ready to cook. If setting aside for a few hours, the soufflé can remain outside at room temperature. If assembling a day ahead, refrigerate and bring back to room temperature before baking.
Bake for 30 to 40 minutes, or until puffy and well browned on top. Although it will stay inflated for quite awhile, it is best served immediately.