First things first, preheat your oven to 400°F (200°C). While that’s heating up, gather a baking dish—about 2-quart size works well. This step sets the stage for your oven-baked creation.

In a skillet over medium heat, melt the unsalted butter. Add the finely chopped onion and let it cook for about 5 minutes until softened. Toss in the minced garlic and cook for an additional minute. The smell is already heavenly!

Sprinkle the all-purpose flour over the onions and garlic in the skillet. Stir continuously for about 2 minutes to cook out the raw flour taste. At this point, things might start getting a bit thick.

Gradually whisk in the chicken stock and dry white wine. This is where the magic begins. Keep whisking until the mixture becomes smooth and starts to thicken. Add the sea salt, pepper, and poultry herb seasoning to elevate the flavors.

Now, fold in the shredded chicken and frozen mixed veggies. Stir everything together and let it simmer for about 5 minutes. This allows the flavors to meld beautifully. The anticipation builds as you watch your filling transform.

If you haven’t done so already, make your creamy mashed potatoes. Boil your potatoes until tender, then mash them with the whole milk, Dijon mustard, and fresh thyme. Season to taste with salt and pepper. They should be creamy but with enough structure to hold their shape when spread.

Now, take your filling and pour it into the bottom of the baking dish. Spread it out evenly. Then, using a spoon or a spatula, dollop the mashed potatoes on top and gently spread them to cover the filling. Use a fork to create peaks. These peaks will brown and crisp up beautifully as they bake.

Pop your assembled pie in the preheated oven and let it cook for about 25-30 minutes, or until the top is golden and bubbling. The scent that fills your kitchen is something you’ll want to bottle up and keep forever.