Soufflés consist of two main parts, whipped egg white and a base. The base provides stability and flavour and is normally made with a crème patisière for a sweet soufflé and a cream base for a savoury soufflé.
It is important that this base has quite a thick consistency as too much water content will prevent the soufflé from rising.
The eggs should be whipped to very stiff peaks. If adding sugar, add half the amount at the start then gradually whisk in the rest.
When mixing the eggs and the base together, it is best to do this in two parts; fold one third of the egg white into the base with a spatula and beat until fully incorporated. Next, very gently fold in the rest of the egg white trying to keep as much of the air in as possible, the air trapped inside the egg white is what makes the soufflés rise in the oven.