*Before you do this achievement, you need to have Gazebo unlocked. I also recommend having VIII - Mad Groove unlocked as well.*

This achievement involves levelling Gazebo's stats by over healing, so you're going to want a lot of floor chicken. For this, choose The Coop and turn on Arcanas and Endless. Choose VIII - Mad Groove from the Randomazzo and start the level.

I found that the quickest way to do this achievement was to break the lights and find Nduja Fritta Tanto, use that to cook the chicken running around and then wait for Mad Groove to teleport all chicken to you. Doing this allows you to collect it all at once and quickly overheal without losing health, which may happen if your just running around trying to find food. You can also use the Fire Wand to cook chickens, which you can pickup after a few minutes.

Since it levels up a random stat each time, it's hard to know which stats are at max so it's best to stop playing once the stat increases stop appearing completely. Then you can exit the game and the achievement is yours and you unlock the Darkana Hidden Anathema (III).