Step 1 (prep and cook turkey)
Preheat oven to 400F
Season your turkey meat with salt, pepper and garlic powder and place in a roasting pan
Melt the butter and then mix in mustard powder, dried sage, dried oregano and dried thyme.
Let butter mixture cool for 5 minutes then pour over turkey pieces.
Loosely tent turkey with foil. Place turkey in oven and immediately turn temperature down to 325 F.
Cook the turkey 20 minutes per pound or until the turkey breast has an internal temp of 170 -175F, basting every 20 minutes. Remove the foil for the last 40 minutes of roasting.
Step 2 (while the turkey is cooking, make your stuffing!)
Place all stuffing ingredients in a large bowl. Mix until well combined. Set aside (alternatively you can use your favourite stuffing mix to make 8-9 cups of stuffing).
Step 3 (make your mashed potatoes)
Place potatoes in large pot and cover with water. Add salt to water.
Bring to a boil with lid off. Turn heat down, cover potatoes and simmer for 10 minutes or until potatoes are tender.
Drain potatoes well - you want them to be dry.
Save 1 cup of potato water for the gravy.
Warm the milk with the ¼ cup butter and add to drained potatoes. Mash really well (I like using a hand-held blender or food processor).
Add 1/4 plain Greek yogurt to potato mixture - stir to combine. Season with salt and pepper if needed. Set aside
Step 4 (Make your gravy)
Remove Turkey from the oven. Place turkey pieces on a cutting board and let cool for 10 minutes.
Pour the turkey drippings into a saucepan. Heat until bubbling and add 1/3 cup flour to make a roux.
Slowly add 1 cup of the saved potato water and whisk until smooth. Add more liquid if needed. Alternatively make your favourite gravy mix (at least 2 cups)
Step 5 (Put it all together!)
Remove turkey meat from bones and slice into large pieces.
Set up an assembly station with the turkey meat, potatoes, gravy and stuffing.
Lightly oil a large 9x13 inch baking dish
Layer stuffing on the bottom and lightly drizzle with gravy.
Layer the turkey meat on top of stuffing. Lightly drizzle with gravy.
Spread mashed potatoes over turkey and drizzle with 1 tablespoon of olive oil.
Cover with foil. Refrigerate overnight.
The next day, bake in a 325 oven for 1 hour. Take foil off for last 20 minutes. Let rest for 10 minutes.
Serve casserole with extra gravy, cranberry sauce and Roasted Vegetables. You can refrigerate casserole for 2-3 days or freeze for up to a month.