Cover tightly with a lid or plastic wrap and refrigerate for at least 2 hours, or up to overnight, to let the marshmallows soften, the coconut plump up, and the flavors blend.
Give the salad a gentle stir just before serving, then scoop into small bowls or onto plates as a sweet side dish.
For kids who are picky about texture, you can chop the mandarin segments into smaller pieces so they blend in more with the marshmallows. If your family likes things a little sweeter, stir in an extra 1–2 tablespoons of the mandarin juice before adding the fruit, or swap half of the sour cream for vanilla yogurt. To make it feel a bit more special for holidays, sprinkle a few extra marshmallows and a pinch of coconut on top right before serving so it looks extra fluffy. If coconut is a no-go in your house, you can leave it out and add an extra 1/2 cup of marshmallows for a simpler, cloud-like salad. This recipe also doubles easily for larger potlucks—just use a bigger bowl and give it plenty of chilling time so everything has a chance to soften and meld together.
