Preheat oven to 400F (200C).

Roll out the pie crust on a floured surface to fit a 9-inch pie dish and transfer it to the dish.

Bake the crust in the oven for 15 minutes until lightly golden.

In a bowl, beat eggs with milk, salt, pepper, and thyme.

Add chicken, spinach, cheese, and mushrooms to the egg mixture and mix well.

Pour the filling into the pre-baked crust.

Bake the quiche for 50-60 minutes until set and golden on top.

Let cool for a few minutes before slicing and serving.