For the chorizo and bean topping: In a large heavy saute pan, heat 2 tablespoons oil on medium-high heat. Add the chorizo and cook until crisp, about 6 minutes. Remove from the heat and reserve. In a large heavy saute pan, heat the remaining 2 tablespoons oil on medium-high heat. Add the beans and cook until warm, about 5 minutes. Remove from the heat and reserve.
For the tortillas: Combine the corn masa, 1 1/4 cups water and salt in a large mixing bowl. Mix thoroughly by hand to form a soft dough, about 2 minutes. If the dough feels dry, add more water (one tablespoon at a time). Preheat a 12-inch cast-iron skillet. Place a piece of parchment paper on a flat surface. Put half of the dough onto the parchment paper and place another piece of parchment paper on top. Using a rolling pin, roll out the dough until it is 1/4-inch thick and 10 inches in diameter. Drizzle the oil into the hot skillet and place the rolled out masa dough into the skillet to cook for about 2 minutes. Turn over to cook on the other side.
To assemble the pizza: Spread 1/2 cup of the warm refried beans onto the cooked side of dough. Add 1/4 cup Oaxaca cheese and 1/2 cup cooked chorizo. Continue to cook for until the cheese is melted, another 2 to 3 minutes. Remove the pizza from the pan onto a round serving platter. Top with the iceberg lettuce. Season with salt and pepper. Then sprinkle with crumbled queso fresco and a drizzle of Mexican crema. Cut into 4-inch squares and serve immediately. Repeat with the remaining half of dough and toppings.