How do I kosher a deep fryer

We have a deep fryer that we only used for meat and sometimes fish. The other day my wife fried what she thought was fish sticks. It turned out to be mozzerala sticks. Is there a way to kosher the deep fryer?

What kind of deep fryer is it? Is this just a very deep pot that you used to deep fry foods or is it some kind of kitchen appliance? If it’s the latter, please send us a picture.

There is no control to make it hotter or colder. You plug it in add oil and you can start to fry. The oil get very hot and we used to fry meat and fish in it. By accident it was used to fry mozzarella sticks. I was reading that I might be able to fill it to top with water then plug it in. when it gets hot and bubbles i should take a rock put it over a fire or bbq until its very hot then put the rock in the deep fryer. Is this correct?

Put in water to the highest level and when the water boils put on a cover on top. You do not need a rock