My friend was in a restaurant where a diner was complaining LOUDLY that the curry was not hot enough, and the chef didn't know how to cook.
The chef emerged from the kitchen with a bottle of clear liquid and a spoon.
"Your curry not hot enough sir? That's OK sir, we can make it a bit hotter if you like sir. I can put some extra heat in sir. Here sir, try this and see how much you think you need."
Hands teaspoon of clear liquid to customer.
Customer (egged on by drunken mates) sips liquid.
Customer is carried out of restaurant by his friends—to the applause of the rest of the patrons!
As the chef returns to the kitchen, my friend intercepts him and asks what is in the bottle.
"Pure Capsaicin. We use it to make the curry as hot as we need to" says the chef with an evil grin.