Heat a large frying pan over medium-high heat and add olive oil. Add onion and sauté until they start to soften.
Reduce heat to medium-low and cook until onions brown slightly, about 7 minutes.
Mix in spinach and garlic and cook for 5 minutes, or until spinach is wilted and cooked. Remove from heat and let cool.
In a large bowl add cooled spinach mix with yogurt, salt and pepper. Mix until combined, cover and refrigerate for 2 hours prior to serving.
When ready to serve, transfer to serving bowl and garnish with walnuts.
Notes
Save a little bit of the sautéd vegetables and use it as a garnish with the walnuts. Serve with pita bread, chips and/or an assortment of vegetables.If using frozen spinach, be sure to thaw completely and squeeze out the excess water before adding to the sautéed onions.TO STORE: Store any leftovers in an airtight container and refrigerate for up to 4 days.TO FREEZE: I don't recommend freezing this as the yogurt's texture changes when frozen and thawed.