This achievement requires that you use the card "Petty Theft" which is found in random Concealed Cavern event to steal 2 treasures from another random Concealed Cavern event that shows a big and small chest. If you don't have the Petty Theft spell you are given the choice to trade health for gold in 2 different amounts. With the spell you get both for free but lose the spell (totally worth it!).
Relying on 2 random events to occur in the same run in the right order is boring though, so why don't we use a seeded run that was posted by Captain Youl on Steam instead?
From the main menu, select:
- Community Challenges - Play
- In the Join Challenge section type in: ProveDriedEnsemble
- Hit the right arrow button
During this run make sure you choose paths with Concealed Caverns whenever possible and you are guaranteed to get this achievement. If you happen to make a mistake you can retry as much as you need.