Add the butter to a saucepan and melt it over medium heat.
Add in the diced vegetables and sauté until the carrots are al dente.
Add in the cream of chicken soup and leftover turkey and mix together.
Allow it to begin to simmer.
Remove it from the heat.
Stir in the peas.
Place the mixture into a casserole dish.
Top with leftover mashed potatoes.
Bake in the oven for about 20 minutes or until the mixture is bubbling.
Optional: broil for 2-3 minutes to make the potatoes crispy.
Top with parsley and serve hot.
Notes
Make-Ahead Instructions: You can assemble the entire casserole up to 24 hours in advance. Cover it tightly and store it in the refrigerator, then bake as directed—adding 5–10 extra minutes if it’s going into the oven cold.
Freezer Instructions: Let the casserole cool completely, then wrap it well or transfer portions to airtight containers. Freeze for up to 3 months and reheat in the oven at 350°F until warmed through.
Cream of chicken soup made from scratch tastes amazing but of course you can use two cans of the premade kind if you want.