Boil salted water in a medium pot.
Add the spinach and stir until it gets wilted (typically three to five minutes).
Drain the wilted spinach and squeeze to remove any excess water --- then chop roughly and set aside.
Heat olive oil on a medium pan over medium-high heat.
Once oil is ready, add garlic and onion and saute until they soften and turn slightly brown.
Add the cinnamon powder and dried mint and cook for a couple of minutes.
Cook for about two minutes. (Note: Keep mixing to avoid burning; lower heat if necessary). Add the chopped spinach and a bit of salt and cook for a couple of minutes, then take off the heat to cool.
Combine the yogurt, salt, and pepper in a bowl --- use a whisk to mix.
Add the spinach from the pan and mix to combine evenly.
Taste and add more salt and pepper, if needed.
Cover your Persian yogurt spinach dip with plastic and place in the refrigerator for at least two hours.
Transfer to a serving plate, and sprinkle with walnuts (or more dried mint) --- enjoy!