Zest from 8 key limes plus more for garnishor 4 regular limes
Line an 8x8 baking dish with parchment paper and spray with cooking spray. This will help remove them easily later. Set aside.
Measure out all the ingredients before you begin this process. Trust me, we’re going to move through this recipe quickly.
In a saucepan, bring milk, sugar, and salt to a boil, while stirring constantly. Don’t walk away or it may burn. Cook for 5 minutes, until the sugar is fully dissolved, then remove from heat. Make sure it’s bubbling before removing it from the heat. That’s what’s going to help the chocolate and marshmallows melt.
Add marshmallows, white chocolate chips, key lime juice, and lime zest. Stir constantly with a rubber spatula until the mixture is smooth. Yes, your arm will hurt from all the stirring. You will probably stir for about 5-10 minutes. Promise, it will be worth it!
Transfer mixture to the prepared baking dish and cool completely. Chill for 3 hours or overnight. Slice into 1-inch squares. Enjoy!