Roll pastry crust into a quiche pan or pie plate and trim the edges. Follow the package instructions for pre-baking the crust. I preheat the oven to 425 degrees, dock the crust with a form, and bake for 10 minutes. Let cool while making the filling. Reduce the oven temperature to 325 degrees.
In a skillet over medium-high heat, add the olive oil and sauté the mushrooms until browned; about 2 minutes. Add the sliced kale and cook until it wilts. Then add the garlic, 1/2 teaspoon salt, and red pepper flakes. Once the garlic cooked; about 1 minute, remove from the heat and let cool and making the custard.
To Make the Custard: In a medium bowl, whisk together the milk, heavy cream, egg yolks, eggs, and remaining 1/4 teaspoon salt. Whisk to combine thoroughly.
To Make the Quiche: Place the pre-baked pastry on a rimmed baking sheet. Sprinkle the grated cheese over the base of the shell. Then add the sautéed mushroom and kale, and top with custard.
Bake the quiche for 45 to 50 minutes. The quiche is done once the custard is set and is lightly golden brown. Let cool for before removing from the tart or quiche pan and serve.
Notes
Greens
While we've used kale in this recipe, other greens like spinach and collard are delicious too. Use your favorite!
Grated Cheese
Use your favorite grated cheese. Swiss, Gruyère, Fontina, or Italian blend cheese are great choices.
Serving Sizes
While you can get 8 to 10 slices from a 9-inch quiche, heartier eaters may like larger slices. Plan accordingly.