The thing to be careful about is the plate you mix the flour and water in. After 18 minutes the dough is hametz (leavened bread).
["How far astray we can go (often with practically disastrous consequences, particularly in medicine and agriculture) when we haughtily ignore the proper names of things, disregard the small but distinctive differences among real species, and falsely assume that all things looking basically alike, and coming from the same broad region, must be the "same" animal."]
That means on Pesach you can have hot oatmeal cereal in the morning. In fact, it is preferable to do your own cooking on Pesach. The matza they sell in stores I would not touch with a ten foot pole.
I should not need proof because this is obvious. However, just to make a point, I want to mention how Hillel would wrap the meat of the Passover offering in matza. How is that possible if it is crunchy?
[This might be the place to clear up another misunderstanding in the New Testament about the leaven of the Pharisees which is hypocrisy, not Talmud. Leaven is not the same thing as bread.]
Therefore the main thing to be careful about is the plate you mix the flour and water in. But the frying pan or pot is no problem because once the mixture has been cooked, it can not become hametz--ever.
Thus the plate you mix the flour and water in has to be washed in cold water before you you it again. This is very important--because the remaining dough in the dish is pure chametz after 18 minutes,