Roast the poblano peppers directly over a gas flame or under the broiler, turning frequently until the skin is completely charred and blistered, about 8-10 minutes.

Place charred peppers in a plastic bag or covered bowl and let steam for 10 minutes to loosen the skin.

Gently peel the skin off each pepper, then make a small lengthwise slit and carefully remove the seeds and membranes, keeping the stem intact.

Stuff each pepper generously with shredded Oaxaca cheese and press closed gently.

For the salsa, roast tomatoes, onion, garlic, and serrano pepper in a dry skillet over medium-high heat until charred, about 10 minutes.

Blend roasted vegetables with broth, oregano, and a pinch of salt until smooth, then simmer in a saucepan for 10 minutes.

Beat egg whites with a pinch of salt until stiff peaks form, then gently fold in the egg yolks one at a time.

Season flour with salt and pepper, then lightly coat each stuffed pepper in flour, shaking off excess.

Heat vegetable oil in a large skillet to 180°C (350°F), testing with a small drop of batter which should sizzle immediately.

Dip each floured pepper into the egg batter, coating completely, and carefully place into the hot oil.

Fry peppers for 3-4 minutes per side until golden brown and crispy, ensuring the cheese inside is fully melted.

Drain on paper towels briefly, then serve immediately over warm tomato salsa, garnished with fresh cilantro and a dollop of sour cream.