Roast the fresh poblanos by placing it over the open flame and turning them from time to time until the outer skin is brown charred and bubbles. Place in a plastic bag and let them sweat, 10 minutes. When cool remove the outer skin by running your fingers down. Do not wash. Make a small incision and remove the inside seeds by making attention to keep the flesh as intact as possible.
Fill the inside of the poblanos with the cheese.
Meanwhile heat oil to the depth of 1 inch.
In a large bowl, beat the egg white until they form soft peaks, but not too stiff and dry. Gradually add the salt and yolks. When they are well incorporated, lights dust one of the chiles with the flour.
With a perforated spoon, or two forks, dip the chile into the beaten eggs and turn it around until it is well covered – not too thin a coating and not too thick. It is useful to have two spatulas or forks to turn the chile around.
Test the oil, should be hot by not smoking, by placing a small amount of batter in the oil. When it sizzles and froth up, the oil is ready. Lower the chile in the hot oil and turn the chile around. When the batter is well set and deep golden color, turn and golden the other side.
Once golden remove from the hot oil and place on a plate with double paper towel to absorb the excess oil.