Melt butter, stir in flour, salt, pepper, cumin and dry mustard.  Cook and stir over medium heat until bubbly.  Remove from heat, blend in milk with wire whisk.  Cook and stir again over medium heat until mixture is thick and bubbly.

Stir in cheeses until they are melted.  Remove from heat, add slowly to beaten egg yolks (start with a spoonful at a time, mixing thoroughly with each addition so as to not cook the eggs).  Stir in the green chile.

In separate bowl, beat the egg whites with cream of tartar in large mixing bowl until stiff but not dry.  Gently fold the cheese mixture into the egg whites.  Pour into ungreased 2-quart soufflé dish.  Bake at 350 degrees for 50-55 minutes.   (Do not open the oven door while baking.)

Serve immediately.