Preheat broiler. Place quartered tomatillos on a cookie sheet and roast for 5 minutes.
Meanwhile, make filling: heat olive oil in a large non-stick skillet. Add onions and saute until translucent, then add garlic and saute for 1 minute. Add chicken, chilies, cumin, and coriander and saute for 2 minutes. Add beer and bring to a simmer; cook until most of the liquid has evaporated. Set aside and let flavors meld.
To finish the sauce, remove the tomatillos from the broiler and preheat oven to 350 degrees F.
Place the roasted tomatillos into a blender with the cilantro, green chilies, and egg substitute and pulse until chunky.
Fill a saute pan about halfway with water and bring to a simmer. Using tongs, dip the tortillas, 1 at a time, into the water quickly. (It should be a quick dunk, which will make the tortillas malleable and easy to roll.) Roll 1/2 cup of the filling into each tortilla and place in a casserole dish. Repeat for remaining tortillas and filling.
Pour sauce over rolled tortillas and bake for 20 minutes. Remove from oven and top with shredded cheeses. Return to oven for 10 minutes or until cheese is melted. Remove from heat, top each serving with 1 teaspoon sour cream, and serve.