If your Easter Chocolate Chip Cookies turned out flat instead of puffy, here are a few possible reasons:

Over-melted Butter: If the butter was too hot when mixed with the sugars, it can cause the cookies to spread too much.
Measuring Flour Incorrectly: Not using enough flour due to improper measuring can lead to flat cookies. Always spoon flour into the measuring cup and level it off.
Overmixing the Dough: This can incorporate too much air into the dough, causing it to collapse in the oven.
Expired Baking Soda: If your baking soda is old or expired, it won’t react properly to create the lift needed for puffy cookies.
Check these aspects to troubleshoot and improve the puffiness of your cookies next time.