1. Whip Egg Whites: If you have a copper egg bowl use that (see Tips: Souffles for explanation), if not add 1/4 teaspoon of cream of tartar to whites. (The whisk attachment on my KA Immersion Blender is the best tool I've found for whipping egg whites or heavy cream.) The whites should form clear peaks that just tip at the top.
2. Lighten Mixture: Mix 1/3 of whites into sauce. This is called "lightening" and makes it easier to add remaining whites without deflating them.
3. Add Sauce to Whites: This is the key technique to a soufflé. Pour lightened sauce into egg whites and casually fold together.
4. Fold Whites into Sauce:Slide a spatula to the bottom of the bowl and lift straight up and fold toward your other hand. Spin bowl a quarter turn. Fold again. Repeat this until most of the whites and sauce are mixed - but don't fixate on a perfectly uniform mixture or you'll kill the bubbles and the soufflé won't rise.