Start by heating a skillet over medium heat and add a tablespoon of olive oil. Sauté diced onion until it becomes translucent and fragrant, about 3-4 minutes.
Add minced garlic to the skillet and cook for another 30 seconds until fragrant, stirring constantly to prevent burning.
Transfer the sautéed onion and garlic to the slow cooker, then add chopped leftover turkey, canned pumpkin, chicken broth, ground cinnamon, and ground ginger.
Stir everything well to combine, then season with salt and pepper to taste.
Cover the slow cooker with its lid and set it to cook on low for about 4 hours, until the flavors meld and the ingredients are hot and tender.
Once cooked, open the lid and gently stir the stew. Check the seasoning and adjust salt and pepper if needed.
Serve the pumpkin turkey stew hot, garnished with fresh herbs if desired, and enjoy a comforting, hearty meal.