Preheat oven to 400° F.
Grease gratin dish. Sprinkle dish with half the parmesan cheese. In a sauce pan, melt butter. Add flour and whisk well. Cook 10 seconds, whisk in cold milk in one stroke. Bring to a boil until thick and smooth, about 2 minutes. Add salt and pepper. Cool for 10 minutes. Beat eggs in a bowl, add in cheese and chives/garlic. Combine with white sauce. Add to gratin dish. Sprinkle remaining parmesan on top. Bake for 30-40 minutes until brown on top.