Roast the poblano peppers directly over a gas flame or under a broiler, turning frequently until the skin is completely charred and blistered, about 8-10 minutes. Place in a bowl, cover with plastic wrap, and let steam for 15 minutes.

Meanwhile, place tomatillos, onion quarters, garlic cloves, and jalapeño on a baking sheet. Broil for 10-12 minutes, turning once, until charred and softened.

Peel the charred skin from the poblanos, then make a small slit lengthwise in each pepper. Carefully remove the seeds and membranes while keeping the stem intact.

Stuff each poblano with strips of Oaxacan cheese, being careful not to overfill. Secure with toothpicks if needed.

Peel the roasted garlic and remove the stem from the jalapeño. Add tomatillos, onion, garlic, jalapeño, cilantro, broth, lime juice, and 1/2 teaspoon salt to a blender. Blend until smooth and set aside.

Place flour in a shallow dish and season with salt and pepper. Lightly dredge each stuffed poblano in flour, shaking off excess.

Beat egg whites with cream of tartar until stiff peaks form. In a separate bowl, beat egg yolks with a pinch of salt, then gently fold into the whites to create a fluffy batter.

Heat 1 inch of vegetable oil in a large deep skillet to 375°F (190°C). Dip each floured poblano into the egg batter, coating completely.

Carefully place battered poblanos in the hot oil and fry for 3-4 minutes per side until golden brown and the cheese is melted. Transfer to a paper towel-lined plate.

Gently warm the tomatillo salsa in a saucepan over medium heat for 3-4 minutes, adjusting seasoning to taste.

Spoon warm tomatillo salsa onto serving plates, place a chile relleno on top, and garnish with crumbled queso fresco and fresh cilantro. Serve immediately.