Position an oven rack directly underneath the broiler and preheat the broiler.
In a small mixing bowl, combine the Mexican crema, hot sauce, lime zest and juice and salt to taste; stir to combine. Set aside to let the flavors meld together.
Heat a large nonstick skillet over medium-high heat. Cook the chorizo and onions, stirring occasionally, until cooked through and slightly browned, about 5 minutes. Remove from the skillet with a slotted spoon to a paper towel-lined plate. Set aside until ready to stuff the roasted poblanos.
Place the poblanos on a baking sheet and broil, turning once, until the skin is blistered and blackened, 4 to 5 minutes per side. Put the charred poblanos in a medium heatproof bowl, then cover with plastic wrap and let steam for 10 minutes. Peel and rub away the skins of the poblanos, then gently dry using a paper towel. Cut a 2-inch lengthwise slit in the center of each poblano and carefully cut out the seeds with kitchen shears, leaving the stems intact.
Stuff each poblano with the chorizo and cheese, dividing evenly. Gently close the opening using 2 to 3 toothpicks to keep the filling from falling out.
In a large skillet over medium-high heat, heat the oil until a deep-fry thermometer reaches 375 degrees F. Position a wire rack on a baking sheet.
Meanwhile, add the egg whites to a large mixing bowl. Using an electric mixer, beat until medium peaks form. With the mixer on low, add the egg yolks and 1 tablespoon flour and mix until completely incorporated. The batter should be smooth and fluffy.
Sprinkle the poblanos with salt, then dredge in the remaining 1/2 cup flour, tapping to shake off any excess; dip into the batter until fully coated. Gently add the poblano to the hot oil and fry in batches to not overcrowd the skillet. Cook until golden brown and crispy, 3 to 4 minutes per side. Transfer to the wire rack to drain. Serve warm on a platter and drizzle with the spicy lime crema and a side of yellow rice, if using.
You can also char the poblanos on a gas stove. Set the burners on high and place the poblanos directly on the flames. Cook the poblanos, turning frequently, until charred on all sides, 7 to 10 minutes.