"Grants the knowledge of heavenly chips, and how to use them to make baking more efficient.
It's a secret to everyone."
The Heavenly Chips wiki page should have a trivia section. Because the last bit of the Heavenly Chips Secret info references the first Legend of Zelda game, where you can find a secret room and someone gives you 100 rupees and says: It's a secret to everyone. And I think there's some other references in the other upgrades I missed.