In a skillet, heat the butter and saute the onion and garlic until soft. Add the corn and oregano and cook for an additional 5 minutes. Remove from the heat and stir in the sour cream and cheese.
Make a slit in the side of each chile and stuff with the corn mixture. Dredge the chiles in the flour and shake off any excess.
Beat the egg whites until they form stiff peaks. Beat the yolks with the water, the tablespoon of flour, and the salt. Fold the yolks into the whites and stir gently.
Dip the chiles in the egg batter and fry one at a time in 1 to 2 inches of oil until they are golden brown.
