Does anyone know how to make the congee like those in Dim Sum/Yum Cha restaurants?
Congee itself is just thick rice porridge. It is usually made with a combination of short-grain and 'sticky' (glutinous) rice, but any kind of white rice will work.
Put 3/4 cup rice (1/2 cup regular, 1/4 cup sticky, if you have it) in a pot with 8 cups of water and a little salt. Bring to a boil and simmer for 1 to 1 1/2 hours, until it is a thick porridge. Stir now and then so it doesn't stick. Many electric rice cookers have a congee setting, which makes everything really easy - just put in a measure of rice, add water up to the congee mark, turn it on and wait.
There are many, many traditional toppings or additions to congee. Eileen Yin-Fei Lo said it well in her "From the Earth: Chinese Vegetarian Cooking": "Virtually any food can be added to one's breakfast congee in China. What you might add to it depends upon your preferences."
Just wanted to offer a cheaper variation to this. Presoak the rice with a tea spoon of salt and a tea spoon of vegetable oil overnight or for half an hour if you're in a rush. Basically, the longer you presoak the rice, the less you need to cook the rice in water before it begins to break apart. Simmer the rice and water solution with additional water, stirring occasionally. You should see the rice gradually thicken until it begins to break apart. About ten minutes after this is a good time to stop. When the rice first begins to simmer, you can add chicken stock and or pieces of chicken leg. Traditional congee often has meat with bones!
Flavour with more salt. Some popular condiments include fried peanuts and freshly chopped spring onions. Stir these in after cooking for a fragrant treat.