Pre-heat the oven to 190°C, 375°F, Gas Mark 5.
Melt the butter in a saucepan. Stir in the flour and blend in mik. Allow to cool slightly before adding the egg yolks, Basil, Garlic Salt, cheese and ham. Mix well. Grease a 1.1 litre (2 pint) soufflé dish. Whisk the egg whites until stiff and carefully fold into the saucepan mixture.
Pour into soufflé dish and cook in oven for 45 minutes to 1 hour or until well risen, golden and firm. Serve immediately with sauté potatoes and vegetables as desired.