Peel and halve onion. Cut halves into ½" dice. Stem poblano pepper, seed, and cut into ½" dice. Stem, seed, and mince jalapeño. Be sure to wash hands, utensils, and cutting board after working with jalapeño. Trim radish, halve, and slice into thin half-moons. Drain and rinse black beans.
Heat olive oil in a medium non-stick pan over medium-high heat. Add onion, poblano pepper (to taste), and half the jalapeño (to taste) (reserve remaining for garnish) to hot pan and stir occasionally, 2-3 minutes. Add corn, black beans, and seasoning blend and stir occasionally, 3-5 minutes. Remove from burner and cool 3-5 minutes.
Spray a large casserole dish with non-stick spray. Pour 1/2 cup enchilada sauce (reserve remaining for topping enchiladas) into prepared casserole dish, coating the bottom. (Use a dish large enough to fit all of the rolled tortillas in a single layer without a lot of empty space) Place one tortilla on a clean work surface. Add ⅓ cup filling to tortilla, tightly roll up, and place in casserole dish, seam-side down. Repeat for remaining tortillas. Don't overfill tortillas. Make sure ends overlap and have a chance to seal while baking.
Place leftover filling around enchiladas or serve on the side. Pour remaining enchilada sauce over enchiladas and top with cheese.
Spray a piece of foil with cooking spray and place over casserole dish, sprayed side down. Tightly seal foil and bake 15 minutes. Remove foil and bake until cheese is bubbly, 7-9 minutes.
Plate dish garnishing with remaining jalapeño (to taste), radish, enchilada sauce, and sour cream. Bon appétit!