Preheat broiler to high. Place peppers on a large rimmed baking sheet and place under the broiler (approximately 6 inches from the element). Roast the peppers until blackened and blistered, turning once after approximately 7-8 minutes. Roast another 4-5 minutes. (If not totally charred, don't worry as you want some texture left.)
Immediately cover with another rimmed baking sheet, aluminum foil or place in a covered container and let cool.
Peel as much of the skin away as you can. Carefully cut each pepper on one side from tip to stem and remove the seeds. Set aside until needed.
Preheat oven to 375 degrees.
Heat oil in a large skillet or saute pan over medium-high heat. Add the onion, reduce heat to medium and cook the onion until beginning to soften, approximately 5 to 6 minutes.
Add the chorizo, breaking it up into small pieces and brown it until no longer raw. Add half the garlic and cook another 1-2 minutes. Transfer chorizo mixture to a paper towel-lined plate to drain. Reserve fat in the pan and reduce heat to medium-low.
Combine remaining garlic, chili powder, cumin, coriander and oregano in the pan. Stir over medium-low heat for approximately 30 seconds or until garlic is fragrant.
Add tomato sauce, water you rinsed the can out with and brown sugar. Bring to a simmer and cook 3-4 minutes just to combine the flavors. Taste the sauce and add additional brown sugar if too acidic. Remove from heat.
Chop one of the Poblanos if they're large or two if they're smaller (whichever one/ones is/are the least pretty).
Combine the chopped Poblano, chorizo mixture, rice, ½ cup of the sauce, half of the cheese and the egg in a large bowl. Mix well.
Prepare a 13 x 9-inch baking dish by brushing it with oil or spraying with cooking spray.
Spread ¾ cup of the sauce in the prepared baking dish.
Fill each pepper with equal amounts of the filling and place in the baking dish.
Pour the remaining sauce over the peppers and top with remaining cheese. Cover loosely with aluminum foil.
Bake for 35-40 minutes. Remove foil and continue baking another 10-12 minutes or until heated through and cheese is melted and beginning to brown.