1. Combine spices and set aside.
2. Combine quinoa and vegetable stock in a pot with a tight-fitting lid. Bring to a simmer over medium heat, reduce heat to low, cover, and cook until liquid is absorbed (about 25 minutes).
3. Place poblano peppers on a wire rack over a foil-lined sheet pan. Roast at 475°F for 5–7 minutes until charred.
4. Transfer peppers to a plastic bag, seal, and rest 5 minutes. When cool enough to handle, scrape skins off with a paring knife.
5. Cut a 2-inch slit lengthwise into each pepper and remove veins and seeds.
6. Heat a large sauté pan over medium heat. Add 1–2 tablespoons water, then onion and garlic, and sweat 3–4 minutes to soften.
7. Add corn, beans, and spices and cook 5 minutes, adding more water if the pan gets dry.
8. Combine cooked quinoa with the bean mixture and chopped cilantro. Stuff each pepper with ¼ cup of the mixture.
9. For service, spread ¼ cup chipotle sauce on a plate, top with 1 chile relleno, and garnish with cashew sour cream, avocado, pepitas, and cilantro sprigs as desired.
10. Cashew sour cream: soak cashews overnight in water, drain, then blend with lemon juice, vinegar, soy milk, nutritional yeast, and salt until creamy. Adjust lemon juice and water as needed and refrigerate.
11. Chipotle sauce: sweat onion and garlic 2 minutes, add remaining ingredients, and cook on low 20 minutes. Remove bay leaf, blend until smooth, and keep hot for service.