Secret Ingredient

If you dare say it's love.

The ingredient that goes in fast food and makes it magically taste good. Without the ingredient, the meal is incomplete and tastes bad. Sometimes, the Secret Ingredient is so secretive, not even its creator knows what it is. Occasionally, at some point, the ingredient is revealed to the audience but no one else. Any rivals of the owner of the Secret Ingredient might try to steal it or recreate it to the best of their ability, only to fail every time.