Keep the oven door closed to preventyour souffle from collapsing whileits cooking.
In French, "souffle" means "puff." Nearly every step in making a souffle is to either increase its puff or protect it from falling. These tips will help you achieve this.
Use a collar. Because a souffle often increases in volume two or three times, a souffle dish needs a collar to hold in the mixture as it bakes and expands.
Remember the acid. A small amount of acid, often cream of tartar, helps prevent a souffle from collapsing. Adding too much acid can interfere with coagulation of the egg proteins during baking though, so follow your recipe instructions carefully.
Beat the egg whites to stiff peaks. The air that is beaten into the whites heats and expands during baking, making the souffle rise.
Gently fold the egg yolk mixture into the egg whites. Use a large rubber spatula and a down-up-and-over motion. Make sure the whites are well incorporated, but don't stir too much or the souffle won't rise very high.
Keep the oven door closed. Opening the door during the first 20 to 25 minutes of baking may cause the souffle to fall because of the sudden influx of cold air.