Roast and prep the chiles

1. Place a rack about 6 inches below the broiler and preheat the broiler to high.
2. Put the poblanos on a sheet pan and broil, turning as needed, until blistered and blackened on all sides, 8 to 12 minutes total.
3. Transfer the peppers to a large bowl and cover with a plate or towel for 10 minutes. Peel off the loose skin, keeping the stems attached when possible, then pat the peppers very dry. Roasting and steaming loosen the skins, and drying the peppers well helps the flour and batter cling better.
4. Cut a slit down one side of each pepper and carefully remove the seed cluster. Stuff each chile with the cheese, leaving enough room to close the seam, and secure with toothpicks if needed.

Make the sauce and batter

1. In a blender, combine the tomatoes, ½ medium white onion, garlic, stock, oregano, and ¾ tsp / 4 g of the salt. Blend until smooth.

2. (Optional) Upgrade: Broil or char the tomatoes, onion, and garlic for the sauce before blending. That one extra move gives the sauce a deeper roasted sweetness and makes the whole plate taste more restaurant-style without changing the basic recipe.

3. Pour the sauce into a medium saucepan and simmer over medium heat for 10 to 12 minutes, stirring now and then, until it tastes mellow and lightly thickened. Keep warm.
4. Put 2 tbsp / 15 g of the flour on a plate. In a clean bowl, beat the egg whites to stiff peaks. In a small bowl, beat the yolks lightly, then fold the yolks, the remaining 2 tbsp / 15 g flour, and the remaining ½ tsp / 3 g salt into the whites just until combined.
5. Lightly coat each stuffed chile in the flour, tapping off the excess. This thin flour layer helps seal damp spots and gives the egg batter something to grab onto.

Fry and serve

1. Pour the oil into a large skillet to a depth of about ½ inch and heat over medium to 375°F / 190°C. If you do not have a thermometer, a small drop of batter should float quickly and sizzle without instantly turning dark.
2. Coat the chiles in the batter and fry 2 to 3 at a time, turning once, until puffed and golden brown, about 2 to 3 minutes per side. Drain briefly on paper towels and remove any toothpicks.
3. Spoon some warm tomato sauce onto each plate or onto a serving platter, then set the chiles on top so the shell stays lightly crisp.
4. Finish with the diced onion, cilantro, and lime wedges. Success looks like a tender pepper with molten cheese inside and a light golden shell that feels airy and delicate rather than heavy.