Fresh Spinach-To make this with fresh spinach, use 1 lb of fresh spinach. Cook down until wilted, about 3-4 minutes. Drain completely before using in the dip.
Make Ahead- You can absolutely prepare this ahead of time; you can mix it up, cover and refrigerate up to one day in advance. It's good for about three days in the refrigerator, but I recommend only making it a day in advance so it's at peak freshness!
Storing-Keep the leftover dip in an airtight container for up to 3 days. I would suggest storing the dip separate from the bread and your best bet is to eat the bread the same day you serve the dip.
Freezing-I don't recommend freezing it, however, because the yogurt and mayo can break down a bit when thawed and cause the dip to be runny.