Preheat and prep: Heat your oven to 375°F (190°C). Grease a 9x13-inch baking dish.

Sauté aromatics: In a large skillet, warm the olive oil and 2 tablespoons butter over medium heat. Add onion and celery, and cook 4–5 minutes until soft. Stir in carrots (if using), mushrooms, and a pinch of salt. Cook 3–4 minutes more. Add garlic and cook 30 seconds.

Cook the veggies: Add broccoli or green beans and cook 2–3 minutes to soften slightly. They’ll finish in the oven.

Make the creamy base: Stir in the remaining 2 tablespoons butter. Once melted, pour in chicken broth and bring to a gentle simmer. Add cream and cream cheese. Whisk until smooth and creamy.

Thicken (optional but recommended): Sprinkle xanthan gum very lightly over the surface while whisking constantly to avoid clumps. Simmer 2–3 minutes until the sauce coats a spoon. Season with salt, pepper, and 1 teaspoon thyme.

Add the chicken: Fold in the cooked chicken and a handful of parsley. Taste and adjust seasoning. The filling should be savory and well-seasoned.

Transfer to dish: Pour the filling into the prepared baking dish and spread evenly.

Make the “crust” topping: In a bowl, whisk eggs. Add almond flour, Parmesan, mozzarella (or cheddar), baking powder, 1/2 teaspoon salt, a few grinds of pepper, and a pinch of thyme. Mix until a thick, spreadable batter forms. If too stiff, add 1–2 tablespoons cream.

Top the casserole: Dollop the batter over the filling, then gently spread to the edges. It doesn’t need to be perfect—some gaps are fine and let steam escape.

Bake: Place in the oven and bake 22–28 minutes, until the topping is set and golden with lightly browned edges. If browning too quickly, tent with foil for the last few minutes.

Rest and serve: Let it rest 10 minutes to thicken. Sprinkle with extra parsley. Serve warm.