Place oven rack in middle position and preheat oven to 350 degrees F. 

For the Cauliflower

1. While cooking the other vegetables and meat, steam or boil cauliflower until very soft. 
2. Drain well then return to the warm pot and let sit for 5-10 minutes. 

For the Meat and Vegetables

1. Heat a large, deep sauté pan over medium heat. Add one tablespoon of oil, mushrooms and onions, cook until mushrooms are soft, and onions caramelize. Remove from pan and set aside.
2. To the same pan, add carrots, parsnips, celery, and the remaining tablespoon oil and sauté until vegetables begin to soften, about 10 minutes. Remove vegetables and return pan to the stovetop. Add ground turkey and cook until fully browned. Drain if necessary. 
3. Return all vegetables to the pot with the ground turkey and season with Homemade Worcestershire Sauce, basil, thyme, half the salt and pepper, and 1/4 teaspoon garlic powder. 
4. Add the chicken broth and stir to combine. Continue cooking until most of the broth has evaporated, then remove from heat.

Putting it Together

1. Place the cauliflower in a food processor with ghee and blend until smooth (you may need to do this in batches, so split the ghee between them). Transfer to a large bowl and stir in nutritional yeast, cheese, and remaining garlic powder, salt, and pepper. 
2. Transfer meat and vegetable mixture to a 9×13″ to create a level layer, then then evenly top with the mashed cauliflower mixture. 
3. Bake at 350°F for 30 minutes (the edges will begin to brown when ready). Let stand 5 minutes before serving.