Steam potatoes for 15-20 minutes or microwave, until soft
Preheat oven to 350 degrees F.
Heat oil in a large sauté pan over medium-high heat. Cook onion until translucent, 2-3 minutes. Add in ground turkey, garlic and spices and cook for an additional 5 minutes.
Add in zucchini, corn, peas, and carrots. Reduce heat to medium-low and cook covered for 5 minutes, or until vegetables soften. Add in spinach, stir, and remove from heat.
While vegetables are cooking, mash potatoes and combine with butter (optional) and salt/pepper
In a 9x13 casserole dish (or similar size), add the ground turkey mixture and spread evenly across bottom. Then spread potato layer on top.
Bake for 25-30 minutes.