1 ½cups(113 g or 4 oz) freshly sliced crimini mushrooms
1cup(40 g) roughly chopped fresh spinach
¾cup(90 g) chopped onion, about half an onion
3large eggs, room temperature
1egg yolk, room temperature
¾cup(180 ml) whole milk, (low-fat works too)
½cup(120 ml) heavy cream
Dash cayenne, optional
1cup(85 g or 4 oz) shredded Gruyère cheese
Partially Baked Crust
Press pastry dough into a 9-inch quiche dish with a rim height of 1 1/4-inches (I love this quiche dish). Press the dough all the way up the sides, folding any overhanging dough in on itself (you can see photos on how to do this here).
Place dough-lined tart pan in the refrigerator to chill until firm, about 40 minutes. Transfer tart pan to the freezer until very cold, about 20 minutes.
While the tart pan is in the freezer, preheat your oven to 375° F. Remove tart pan from the freezer and double line it with aluminum foil. Place pie weights on top of the foil. Bake for 30 to 35 minutes or until light golden in color. Transfer to a wire rack to cool. Keep oven on and prepare filling.
In a skillet, melt butter over medium heat. Cook onion and mushrooms until tender, about 5 minutes. Add spinach and cook just until wilted. Remove from heat.
In a large bowl, vigorously whisk eggs and egg yolk. Add milk, heavy cream, salt pepper, cayenne and whisk until combined. Stir in cooked vegetables and Gruyere cheese.
Transfer filling to partially baked crust. Bake quiche at 375° F for 40 minutes or until a knife inserted in the center comes out clean and the center barely jiggles when gently shaken. All the quiche to sit for 10 minutes before cutting and serving.
Frozen spinach may be used as a substitute. Defrost the spinach and ring it completely dry otherwise your quiche will be watery. Add it to the mixing bowl with the filling ingredients and stir until incorporated.Store spinach mushroom quiche covered in the refrigerator for 3 days.How to freeze spinach mushroom quiche: Let the quiche cool completely in the pan, then freeze for 2 hours to set. Remove the quiche from the pan, wrap in plastic wrap, then aluminum foil to prevent freezer burn. Store in the freezer for up to 2 months. Defrost in the refrigerator overnight before reheating.How to reheat quiche: Preheat oven to 350 F. Cover quiche with aluminum foil and bake for 15 minutes or until heated through. If reheating a frozen quiche, bake for 30 to 40 minutes.