One of my hundred-year-old cookbooks has a recipe for chicken souffle, and I had some left-over chicken so decided to give it a try. The Chicken Souffle was lovely. The recipe called for chopped onions, thyme, and parsley, and they added a nice flavor to the dish.
Here’s the original recipe:

The old cookbook does not give an oven temperature for baking the souffle. When I made this recipe, I baked it at 350° F. The recipe says that this needs to bake for only 20 minutes, but it took close to 40 minutes for it to set and ligthtly brown when I made it. Maybe the author used a higher temperature.
Here’s the recipe updated for modern cooks:
Chicken Souffle
1 cup cooked chicken, chopped
2 eggs, separated
2 tablespoons butter
2 tablespoons onions, finely chopped
2 tablespoons flour
1/2 teaspoon salt
dash pepper
1/4 teaspoon thyme
1/2 teaspoon dried parsley
1 cup milk
Melt the butter in a sauce pan, and stir in chopped onions. Sauté for several minutes until the onions are transparent. Stir in the flour, salt, pepper, thyme, and parsley. Gradually, add the milk while stirring constantly. Continue stirring until the white sauce thickens. Remove from heat.
In another bowl, beat egg yolks until smooth. Add a tablespoon of the hot sauce to the beaten egg yolk and stir quickly. Repeat with another tablespoon of the sauce. Then add the egg mixture to the sauce and quickly stir. (This helps keep the egg yolks from cooking when they are stirred into the sauce). Add the chopped chicken and stir again. Allow the mixture to cool. (I put it in the refrigerator for a few minutes.)
In the meantime, preheat oven to 350° F. Put the egg whites in a mixing bowl and beat until peaks form. Then fold the beaten egg whites into the chicken mixture. Put in a 1-quart baking dish. Place in oven and bake until the souffle is lightly browned (about 30-40 minutes). Remove from oven and immediately serve.