Make the filling: Heat a large pan over high heat until very hot and add the mushrooms and the olive oil. Cook the mushrooms until browned, about 5-6 minutes.
Reduce heat to medium/high and add the onion, the garlic, the thyme, the bell peppers, the bay leaf, the salt, and the pepper. Stir until vegetables are soft, about 5 minutes and turn off the heat.
Transfer the potatoes, red beans, olives, parsley, tomato, cumin, green onions, and olive oil to a food processor and process until everything is mixed (you can also skip the food processor and mash everything with a fork for a more “rustic” texture). Mix the red bean mixture with the vegetables.
Take two-thirds of the dough and roll it out forming a circle large enough to cover the bottom and sides of a 9-10 inches (25 cm) pie pan. Use some extra flour if needed.
Lightly oil the pan and cover with the dough. Fill the pie with the filling and roll out the rest of the dough in a circle large enough to cover the surface of the pie.
Brush the sides of the pie with some water and cover with the second circle. Trim the edges and use the trimmings to make some decorations (optional).
Bake for 50 minutes or until golden brown. For better serving let the pie cool for 20 minutes before cutting it.