Preheat oven to 350ᵒ F.
In a skillet, sauté scallions and garlic in vegetable oil. Add mushrooms and sauté briefly.
Stir in olives or beans and cook over medium heat for 2 to 3 minutes.
Press liquid from spinach with your hands. Add spinach and salt to skillet. Stir to mix and heat through.
Reserve one cup of enchilada sauce and pour remaining sauce into wide bowl. Place two 8- or 9- inch pie plates next to the bowl. Dip 8 of the tortillas in the sauce, one by one, coating both sides. After each coating, lay the tortillas on the bottom of the pie plates, overlapping as necessary. You will have 4 tortillas lining the bottom of each pan.
Divide the sautéed mixture between the pans, covering tortillas. Sprinkle ½ cup of cheese over the filling in each pan. Dip remaining 8 tortillas, again coating both sides, and overlap them on top of the cheese. Spread any remaining sauce over tortillas and top with remaining cheese. Bake pies at 350ᵒ F. for 35 to 40 minutes.
After baking for 25 minutes, pour reserved enchilada sauce onto the pie and continue baking for 10-15 minutes. Test pie after 35 minutes. To test, insert a knife into the pie. If the tortillas are soft, the pie is done. If they still feel stiff, bake for another 5 minutes.