First, make the crust.
Add flour, butter, baking powder, and salt to large food processor and pulse until butter is evenly distributed.
Add the water and pulse until dough forms.
Dump crust dough onto a clean surface and if it still seems too dry, sprinkle a teaspoon of water at a time until it is a workable dough but not sticky.
Roll out into a rectangle and then fold in half.
Repeat this 3 more times, and then wrap in plastic wrap and refrigerate while you make the quiche filling.
Alternately, you can make the crust dough in advance, just remove from refrigerator about 30 minutes in advance if it has been refrigerated for more than 2 hours.
Next, prep the vegetables and preheat your oven to 350 degrees F.
Begin by defrosting the spinach and wringing out as much of the water as possible. This is important because if you don’t get enough of the water out, your quiche could be soggy.
Next, add olive oil to a large skillet over medium-high heat.
Add onions and red bell pepper and cook for about 3 minutes, until they begin to soften.
Add mushrooms and garlic and stir well to combine.
Season with salt and pepper.
Cover and cook for 8-10 minutes, stirring occasionally, until all vegetables are softened and cooked.
In a medium bowl, combine cream cheese and 1 egg and whisk until well combined and creamy.
Add remaining 2 eggs and whisk until well combined and creamy.
Add milk to egg/cream cheese mixture and whisk until combined.
Now it’s time to assemble the quiche.
Take your crust out of the refrigerator and roll out on a lightly floured surface into a 12-inch round.
Trim the edges if needed.
Press the crust into a 9” pie dish.
Place vegetable mixture from skillet in crust shell and then evenly distribute with the spinach.
Sprinkle with cheese and then pour egg mixture over the cheese.
Bake in preheated oven for 65-70 minutes, until crust is golden and quiche is set through the middle.
Let stand for 10 minutes before cutting into it.
Serve and enjoy!