Place a large stock pot over medium-high heat and add the butter to the pot. Once the butter has melted, add the onions, poblano peppers and garlic and sauté for 3-5 minutes to soften.
Add the mashed potatoes and broth to the pot. Whisk to dissolve the mashed potatoes into the broth, and bring to a boil. Simmer for 15 minutes.
Add the chopped turkey and orzo stuffing and simmer another 5 minutes. Salt and pepper to taste.