In a medium nonstick skillet, heat 2 teaspoons oil. Add onion and cook, stirring often, until soft but not browned, 3 minutes. Add broth and bring to a boil. Gradually stir in cereal and cook, stirring, until thickened, 4 minutes. Remove from the heat and let cool.
Broil the chiles on a broiler pan until well blistered on all sides, about 2 minutes. Place in a heatproof bowl and cover with plastic to allow chiles to steam. Lower the oven heat to 400°F.
When cool enough to handle, pull the skins off the chiles, being careful not to remove the stems. Slit the chiles lengthwise and carefully remove the seeds, leaving stems intact; discard seeds.
Mix the cheese with the cooled cereal mixture, and shape into 4 “logs,” to fit inside each chile. Carefully stuff each chile with the cereal mixture, pressing sides to close.
In a medium bowl, whisk egg white until it forms frothy white peaks, about 4 minutes. Gently whisk in egg yolk, then sprinkle in and which in flour.
Heat the remaining 1/4 cup oil in a medium nonstick skillet. Dip chiles carefully in beaten egg mixture to coat on all sides, then place seam-side-down in skillet. Cook, turning once gently, until golden on both sides, 3 minutes.
Place chiles in the broiler pan and back until the filling is soft and runny, 8-10 minutes