Move an oven rack to the very top and then turn the broiler on. Place the poblanos on a baking sheet. Add the jalapeño as well if you're making the optional crema. Broil the peppers for 5-7 minutes. Flip them over and roast them for another 5-7 minutes. The skins should be mostly darkened and bubbling when done.
Put the poblanos in a glass dish or plastic bag. Seal the dish and let them steam for just 5 minutes.
Meanwhile, make the avocado crema if you're using it. Cut the stem off of the jalapeño. Add it to the blender along with the rest of the crema ingredients. Blend them for 2-3 minutes until it’s smooth and creamy.
Gently peel the skins off the poblano peppers. Cut a slit down each pepper and remove the seeds. You can do this with a spoon.
Pour the oil in a sauté pan. Turn the heat on to medium-high. Stuff each poblano with ¼ cup of shredded vegan cheese. Then, use toothpicks to close them.
Mix the flour, cornmeal, cornstarch, and salt together in a large bowl. Add the plant milk and stir until combined.
One at a time, dip each stuffed pepper into the batter and then flip it so that it’s completely coated.
Test that the oil is hot enough by dropping some batter into it. The batter should sizzle when it hits the oil. Gently place one stuffed pepper into the oil at a time. Fry them for about 3 minutes on each side or until golden brown.
To serve, remove the toothpicks and spoon a layer of red chile sauce onto a plate. Place the chile relleno on top and then drizzle vegan avocado crema on top. Garnish them with cilantro and enjoy!