Add milk all at once, and cook over medium heat, stirring till mixture thickens and bubbles. Remove from heat; add cheese; stirring till cheese is melted.
Beat egg yolks till very thick and lemon colored. Slowly add cheese mixture, scallions and chives stirring constantly: cool slightly. Gradually pour over beaten egg whites, folding together thoroughly.
Pour into a GREASED 1 1/2 quart souffle dish or casserole.
Bake in slow oven, 300° for 1 hour and 15 minutes, or till a knife comes out clean. Serve IMMEDIATELY.