“The most literal answer is the best”
Bach’s spoon is much like occams razor “the simplest answer is the best”. As he pulls out a big spoon as a witty reply to his friends comment “only a spoonful”. Bach acknowledges that a “spoonful” is only an abstract form of measurement therefore he subverts expectations by pulling out a large spoon. This spoon being full would drain the contents of the tub of ice cream due to its size. Bach can only come to this answer by pushing “spoonful” to its most literal definition. His friends language makes it so that Bach is able to exploit the agreement without voiding the terms of “a spoonful". Therefore making the most literal answer the best one.
"My doctor said I should limit myself to one cup of coffee a day so I employed the principle of Bach's spoon and bought a 32 ounce coffee cup".