Begin by seasoning the chicken strips generously with sea salt and black pepper. Dredge the seasoned chicken in all-purpose flour until thoroughly coated. In a large skillet, heat a splash of olive oil over medium-high heat. Add the chicken strips to the pan and sauté for 3-4 minutes on each side, or until they are golden brown and cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, add a bit more olive oil if needed, then toss in the thick-sliced mushrooms and diced onion. Sauté for about 7-8 minutes until the vegetables become softened and golden. In the last minute of cooking, add minced garlic, stirring continuously until fragrant.

Reduce the heat to medium and add butter to the skillet, allowing it to melt. Whisk in a couple of tablespoons of flour to create a roux, cooking for about 1-2 minutes until bubbly. Gradually pour in chicken broth while continuously whisking to prevent lumps. Next, mix in fresh lemon juice and half and half. Let the sauce simmer for around 3-5 minutes until it thickens and becomes creamy.

Layer the sautéed mushrooms and onions evenly over the cooked chicken in a large casserole dish. Pour the luscious sauce over the top, ensuring everything is well covered.

Cover the casserole with aluminum foil to retain moisture during baking. Preheat your oven to 350°F (175°C) and place the covered casserole dish on the middle rack. Bake for 45 minutes, removing the foil in the last 5-10 minutes to let the top gently brown and bubble. Allow it to rest for a few minutes before serving, garnished with fresh parsley or thyme.