There are three key elements to great scrambled eggs:

1. Good, fresh eggs - doesn't really need explanation does it?
2. Add fat - doesn't really matter if you use butter or cream, I prefer to add butter myself.
3. Slow cooking - the creamy texture comes from creating an emulsion of cooked egg mixed with the added fat, if you try to cook them too fast then the egg will overcook and split from the added fat.


My usual technique is this:-

I chuck a big (50g for 4 eggs) nob of butter in a thick bottomed saucepan and put it over the lowest heat I can whilst I crack and lightly beat the eggs. Season the beaten eggs and pour into the melted butter, then keep stirring gently until the mixture is nearly cooked. At this point turn off the heat, and just let the residual heat in the pan finish the cooking process. It is really important to make sure that the egg mixture doesn't catch on the bottom of the pan, so as you stir make sure that nothing gets the chance to stick.