Touch it and find out! The goal with the bottom layer is to be cool, and you’ll be able to see if it is warm at all by placing your hand on it briefly. For the middle layer, you want to ensure the mint layer has set so that the next layer will sit on top of it. Again, give it a light poke and if it is cool and hard you are ready to add the next layer. If any of the mint layer comes off on your finger, it needs to chill longer. The top layer is a chocolate ganache that needs to re-harden after being melted and spread across the top of your bars. If you poke the final layer and have chocolate on your finger, or leave an obvious fingerprint, it’s not ready yet.