Fill a large pot with water and add the chopped sweet potatoes. Over high heat, bring water to a boil. Reduce heat and simmer the potatoes until fork tender and nearly falling apart. Remove from heat and drain water using a large strainer. Return potatoes to the same pot and add the pureed butternut squash, milk, butter, sour cream and salt. Mash with a potato masher until smooth and creamy. Set aside.
note: if you're butternut squash is not previously pureed, simply peel, seed and chop your butternut squash into 1-inch pieces and boil them along with the potatoes.
Preheat oven to 400 degrees F.
Add one tablespoon of olive oil to a large saute pan and heat over medium-high heat. Add the ground turkey and a dash of salt and pepper. Continue to cook over medium heat until fully cooked. Remove from heat and set aside.
In the same saute pan over medium-high heat, add 1 tablespoon of olive oil to your pan. Add the chopped onion and saute for 1-2 minutes. Turn down heat to medium-low and add the minced garlic and grated ginger. Mix the garlic and ginger with the onions and saute for an additional minute or so. Now mix in the mushrooms, peas, corn and carrots and cook for 5-7 minutes. Stir in the chopped chipotle chilis, adobo sauce and worcestershire sauce, as well as the pre-cooked ground turkey. Mix well.
Creating a well in the middle of your pan, whisk in the flour with the juices from the veggies and meat. Once a paste is formed, slowly whisk the chicken broth in with the flour paste and finally mix in the tomato paste. Mix everything together well. Allow meat and vegetable mixture to simmer on low for 10 minutes or so, stirring occasionally.
Lightly spray a large casserole dish with non-stick cooking spray. First pour the meat and vegetable mixture into the bottom of the dish and top with a layer of mozzarella cheese (I probably used 2 cups because I love cheese). Carefully spread the sweet potato/butternut squash mash evenly over the top of the cheese. Use a fork to scrape the top of the potatoes to make ridges.
Bake for 25 minutes, or until potatoes turn golden and start to bubble at the corners. Allow it to cook for 10 minutes before serving.