For the crust, whisk together flour, cornmeal, 1½ teaspoons salt and baking soda. Combine avocado, sour cream and 2 tablespoons milk. Stir avocado mixture into flour mixture with a fork. If the dough looks too dry, add more milk, one tablespoon at a time, until it holds together when mixed. Turn dough out onto a work surface and lightly knead in any loose flour. Divide dough into 2/3 and 1/3 amounts for the top and bottom crusts; wrap each in plastic wrap, flatten into discs and chill at least 30 minutes.

Preheat oven to 425°. Spray a 9-inch deep-dish pie plate with nonstick spray or coat with butter. Roll the larger dough portion between two floured pieces of parchment or waxed paper into a 13-inch diameter circle; transfer to prepared pie plate. Roll remaining pie dough between parchment and chill both doughs while preparing filling.

For the filling, in a large sauté pan over medium-low heat, heat the olive oil. Add scallion whites, poblano, and garlic; heat until soft, about 5 minutes. Stir in cumin and coriander; cook 1 minute. Stir in beans and heat to warm through, then stir in tomatoes and corn; cook to evaporate any juices in the pan.

In a small bowl, combine ½ cup sour cream and ¼ cup milk; stir into bean mixture in pan. Stir in rice until fully incorporated, then stir in 1 cup cheese, lime zest, juice, cilantro and hot sauce. Chop green tops of scallions and stir into filling. Season with salt and pepper.