
Preheat your oven to 400 degrees f.
Grease a large baking dish lightly with a very small amount of avocado oil or olive oil.
Melt the butter in a large pot over medium heat. Saute the onion, carrots, mushrooms, and garlic for around 5 minutes, stirring frequently.
Meanwhile, in a small dish, whisk together your flour and stock until there are no visible lumps.
Pour this stock slurry over the sauteed veggies, then stir in the coconut milk and mustard.
Add in your cooked chicken and frozen peas, then stir to combine.
Allow the sauce to simmer over low heat for a few minutes until it begins to thicken. Transfer your creamy chicken mixture into a baking dish using a spatula to get everything into the dish.
Arrange your potato slices nicely over the sauce in the dish as shown and baste with the melted butter.
Season with sea salt and pepper. Bake in your preheated oven for 30-35 minutes or until the potatoes are tender and golden.
During the last minute of baking time, you may want to turn your oven up to high broil in order to create nicely browned crispy potatoes.
Sprinkle with fresh chopped parsley if desired.
Allow your beautiful creation to sit for a few minutes to cool just a bit before serving.