Heat a griddle on medium-high heat. Cook the poblano peppers until all sides are charred, turning every few minutes.
Seal the charred peppers in a plastic bag, and let rest for about 15-20 minutes
Remove the chiles from the bag, and peel the skin off. Slice a vertical line down one side of each chile, starting from the stem down to the tip.Remove the seeds with a spoon or your hand. Stuff each pepper with 2-3 strips of mozzarella cheese.
In a large bowl, add egg whites and use a handheld mixer to whip until fluffy and soft peaks have formed. Add the egg yolks and whisk until just combined. Set aside.
Pre-heat a large skillet on medium-high heat, with about 1.5" of oil for frying.
Place the stuffed pepper in the bowl of flour-mixture, pat the flour mixture on the pepper until completely coated. Next dip the floured pepper into the egg-mixture, making sure to hold it closed the whole time. Once coated all around, lay it in the frying pan.
Fry the peppers until they are golden brown on both sides, about 3 minutes per side.
Place one pepper on a flour tortilla, spoon on the salsa and enjoy!