Suppose, for example, that some oatmeal is fixed in gel, or some other substance. A portion of the substance-with-oatmeal is then removed and added to cold milk or some similar dairy product, where it quickly dissolves, yielding a standard bowl of milk and oatmeal. Is there such a substance?
Ideally, the substance should be unobtrusive to the eating experience. This also means that it should not dilute the milk significantly. Otherwise, some taste, colour or odour may be permissible, provided it does not clash with the taste of the meal.
The substance should also not soak the oatmeal, which is why it may not be a liquid.