Add the garbanzo bean flour and 1 cup water to a medium bowl and whisk well. Add 1 tbsp olive oil and ⅛ tsp salt. Whisk batter again and set aside until step 4.
Set the oven to broil on high. Thinly slice just half of the onion. Add the sliced onion and corn kernels to a baking sheet and toss with 2 tsp olive oil and as much of the chipotle powder as you’d like. Broil until browned in places, about 3 to 6 minutes.
Peel and dice the remaining onion. Peel and mince the garlic. Remove the tomatillo husk and rinse and dice the fruit. Finely chop the cilantro leaves and stems. Trim, deseed, and mince the jalapeño. Combine the diced onion, diced tomatillos, chopped cilantro, minced jalapeño, juice from just half the lime, and a pinch of salt in a medium bowl.
Set the oven to broil on low. Place a large ovenproof skillet over high heat and add 1 tbsp olive oil. Once hot, whisk the batter again, add to the hot skillet, and tilt to cover the entire pan. Cook, undisturbed, until socca begins to bubble, about 4 to 5 minutes. Transfer the skillet to the oven to broil until crisp, about 4 to 6 minutes more.
Drain and rinse the black beans. Once the socca is browned on the edges, remove from the oven. Spread just half of the ranch dressing over the crust. Top with roasted corn and onions, about half of the black beans, and mozzarella. Return socca pizza to the oven to broil until the cheese melts, about 2 to 4 minutes.
Transfer the socca onto a cutting board and top with tomatillo salsa and baby arugula. Drizzle Mexican Socca Pizza with remaining lime juice and ranch dressing and cut into 6 pieces. ¡Buen apetito!