1Bring water to boil in large saucepan. Remove from heat; add tomatoes and chiles. Cover. Let stand 20 minutes. Drain, reserving 1 cup of the soaking liquid.
2Heat 1 tablespoon of the oil in medium skillet on medium heat. Add onion and garlic; cook and stir 5 minutes until softened. Transfer onion mixture to blender container. Add tomatoes, chiles, and reserved 1 cup soaking liquid. Cover. Blend on high until smooth. Strain mixture through fine mesh sieve.
3Heat remaining 1 tablespoon oil in large saucepan on medium heat. Add pureed tomato mixture; bring to simmer. Meanwhile, place pinto beans, stock and salt in blender container. Cover. Blend on high until smooth. Stir bean mixture into saucepan. Return to simmer; cook 20 minutes until slightly thickened.
4Ladle into serving bowls and drizzle with Mexican crema and sprinkle with crumbled Cotija cheese. Serve with tortilla chips and sliced avocado, if desired.