For the chicken filling: Heat the oil in a large saucepan over medium-high heat. Add the tomatillos, garlic, jalapeno, onions and 1 teaspoon salt. Cook, stirring occasionally, until soft, about 15 minutes. Add the canned chiles, cumin and 3/4 cup water and bring to a boil. Season with salt and pepper. Reduce the heat, cover and simmer for 10 minutes.
Transfer the sauce to a blender (or use an immersion blender) and puree until smooth. (When blending hot liquid, first let it cool for 5 minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.)
Pour the sauce back into the saucepan (if using a blender) and add the chicken, corn and beans and warm through. Taste and season with additional salt and pepper if needed.
To serve, toast the tortillas over an open flame until just slightly charred (alternatively, wrap in a damp paper towel and microwave for 1 minute to heat through and make pliable). Add about 3 tablespoons of the chicken filling to each tortilla, top with a drizzle of crema, sprinkle with queso fresco and some sliced radishes.