In Hot Water

The following is based on a true story.
Nathan comes home from his out-of-town dormitory. He loudly declares, “I’m starving!” His mother gently reminds him that he managed for a few months on his own and surely he can fend for himself. Nathan, who is famous for his hot dogs, decides to make some for himself.
He looks around the kitchen and sees, to his delight, a utensil with boiling-hot water. He drops two hot dogs in and waits for them to be ready. His mother enters the kitchen and sees Nathan waiting for his food. She grills him: “Where exactly did you cook your hot dogs?”
“Right over there in that stainless-steel utensil.”
His mother screams, “Nathan, you are in hot water! You just made my urn fleishig!”
Nathan says, “Let’s be frank with each other; I’ll just empty out the hot water and put in new water and it will be fine!”
His mother replies, “I’m sorry, but that doesn’t cut the mustard. Even if I change the water, my urn is still fleishigs.”