Cooking is something that very small children do enjoy, though their input is a little limited it's not impossible for them to help.
Our child started stirring soup, mixing dough, and putting icing on cookies around the age of three. When he was four he started chopping tomatoes, and placing them on pizzas, as well as the other toppings.
I'd not trust him to touch an oven, though he sometimes watches the cooking occur and says "Daddy it's ready now", but I do let him stir things in a wok, or chop carrots/cucumbers/similar things.