Preheat the oven to 350°F (175°C).
Sprinkle 1/4 cup of shredded cheddar cheese in the unbaked pastry shell.
In a bowl, mix 1 cup of diced cooked chicken, 1 cup of chopped spinach, and 3/4 cup of shredded cheddar cheese.
Transfer the chicken mixture to the pastry shell.
In another bowl, whisk 3 eggs, 3/4 cup of half-and-half, 1/2 cup of mayonnaise, 1/4 teaspoon of salt, 1/8 teaspoon of ground black pepper, a pinch of salt-free seasoning blend, and a pinch of herbes de provence.
Pour the egg mixture over the chicken mixture in the pastry shell.
Bake in the preheated oven for 35 to 40 minutes, or until a knife inserted into the center comes out clean.
Let the quiche stand for 15 minutes before slicing and serving.