Purloin Sirloin

Α food that marks a rite of passage for a culture in your world
Top sirloin, from cow not rat, is affordable only to those in the Rich Districts. To steal a fully cooked meal that includes sirloin marks the transition of a thief's career from boy to man. Able to steal fat for more than just himself. Able to provide beyond mere subsistence. A man worthy of being a full contributing member of the Thieves Guild.

The rules are simple, the thief has one week to scout and plan a solo heist, the end result needs to feed himself and the four Thieves Guild judges. The thief cannot do any of the cooking or preparing of food, the only work he is allowed to do is to steal.
The plan must be presented to the judges and must be vetted by them first. They check if the plan interferes with any protection agreements that are currently valid, though those usually have clauses that small amounts of food are exempt from protection. Even a low ranking thief must eat, and the Guild certainly isn't going to open its coffers if there is no gain in it.
The test serves as a perfect testing ground for young thieves. The stakes are low so most households know to use only minimal force, angering the Thieves Guild by harming new thieves is never a wise investment. The thief must exhibit more than manual skill, it's a balance of risk and reward. Richer estates will have more guards but excess food granting more time before the servants get suspicious.
For many thieves, this is their first contact with higher members of the Guild and first impressions remain paramount. This is there one shot personally impress them and not hope good word travels up the chain of command. How much extra risk will a young thief take to grab one more bottle of wine? No matter the gold one acquires, free meals remain the sweetest.