Prepare the broth: Heat water in a small pot. Add serrano peppers, tomatoes, onion, and garlic. Cook until chilies start sweating. Remove tomatoes to cool.
Prepare the chili and cheese mixture: Peel and clean the chilies from inside. Chop chilies and panela cheese into small cubes. Add chopped chilies and cheese to the pot with the broth. Add 3 tablespoons of flour and boil to thicken.
Prepare the egg batter: Beat the egg whites with salt until stiff. Add the yolks and 2 tablespoons of flour, then beat again until combined.
Combine batter and chili mixture: Add half of the egg batter to the chili and cheese mixture, mix well, then add the remaining half and mix again.
Cook the pancakes: Heat oil in a skillet. Pour batter to form pancakes and fry until golden and cooked through. Remove and drain excess oil.
Prepare the sauce: Grind tomatoes, garlic, and onion. Heat oil, add a slice of onion, then add the ground sauce and broth. Add cilantro sprigs for flavor.
Serve: Place the cooked pancakes in the sauce to warm through. Serve with rice or as desired.