First make the crust. In a food processor, pulse the flour, salt, thyme leaves, and butter.
Add cold water, 1 T at a time until dough forms together in a ball shape. Remove from food processor and wrap in plastic wrap. Chill for 1 hour.
To get started on the filling, saute the spinach in 1 T of olive oil until completely cooked through. Set aside. Saute the mushrooms in the remaining olive oil until cooked through, and set aside. Once cooled, try to squeeze as much liquid out of the spinach as possible, and drain the juices from the mushrooms. Mix together the cream, milk, eggs, salt, and pepper in a large bowl, set aside.
Spray a spring form pan well on bottom and sides. Sprinkle a little flour on work surface and roll out your dough between 1/8” and 1/4”. Roll your dough onto your rolling pin and gently un roll ontop of the springform pan. Quickly work the sides down without ripping the dough. Form to edges as much as you can. The dough will not reach the top and that’s ok, just as long as you’ve got it high enough to cover the egg filling.
Chill the dough in the spring form for 10 minutes.
Preheat oven to 375 degrees F.
Once dough is firm, start filling with spinach, mushrooms, then cheese. Add egg mixture last.
Bake in oven for 45-50 minutes, or until it doesn’t jiggle in the center.
Cool in the refrigerator for 30 min to 1 hour.
Remove edges from springform, slice, and enjoy!