Directions

1. Preheat oven to 425°. Place tomatoes, onion and serrano on a rimmed baking sheet. Drizzle with oil; toss to coat. Roast until vegetables are tender and lightly browned, 15-20 minutes. Let slightly cool. Place broth, vegetables, garlic, cilantro and salt in a high-speed blender; puree until smooth. Set aside.
2. To make peppers, preheat broiler to high. Place poblano peppers on a foil-lined baking sheet. Broil peppers 4 in. from the heat until skins blister, 4-5 minutes. With tongs, rotate peppers a quarter turn. Broil and rotate until all sides are blistered and blackened. Immediately place peppers in a large bowl; cover and let stand 10 minutes. Peel off and discard charred skin. Cut a slit lengthwise down the peppers; discard seeds.
3. Stuff peppers with cheese; secure shut with toothpicks. Pour oil into a cast iron skillet 2-in. deep; heat to medium-high.
4. Place egg whites in a large bowl; beat on high speed until stiff peaks form, 3-4 minutes. On low speed, beat in egg yolks until smooth. Place flour in a shallow bowl; stir in salt and pepper. Dip stuffed peppers in the flour mixture, then egg mixture. Place in hot oil; fry until batter is golden brown and crispy, 4-5 minutes per side. Transfer to a paper towel-lined plate or baking sheet to drain. Repeat with remaining peppers. Remove toothpicks from fried peppers.
5. To serve, spoon red sauce in shallow bowls; top with fried peppers. Sprinkle with cilantro and Cotija cheese. Serve immediately.