CHILE RELLENOS: Combine the grated manchego, panela and a?ejo cheeses in a bowl and reserve. Working on a towel-lined counter, spread open 1 chile at a time. Mold 1/2 cup of the cheese mixture in your hands to form a compact torpedo-shaped log and place inside the chile. Roll the flesh to entirely enclose the cheese, using the towel to help shape a tight roll. Place on a platter and stuff the remaining chiles. (They can now be reserved for up to 2 days, well covered, in the refrigerator.) Preheat oven to 350F. Spread the flour on a platter. Beat the eggs with the salt and pepper in a bowl wide enough for dipping. Heat the oil in a 9-inch cast-iron skillet over medium-high heat until hot. Dip 3 chiles at a time in the flouor, patting off the excess so just a fine even coating remains. Then place in the eggs. Test the oil by dropping in a bit of egg. If it sizzles immediately and rises to the surface, the oil is ready. Drop the chiles, 1 at a time, into the oil, putting an extra dollop of egg batter on each. Fry 3 at a time until golden brown all over, about 1 1/2 minutes per side. Drain on paper towels. Reheat oil and repeat with remaining chiles. CREMA: Whisk the cream and buttermilk together. Cover and set in a warm place (a gas oven with just the heat from the pilot light is fine) for 8 hours. Crema may be kept in the refrigerator as long as a week. NOTE: Manchego Cheese: There are two kinds of manchego used in mexican cooking - and neither is the high-priced Spanish variety sold in upscale cheese shops. There is a hard variety (called viejo) and a soft, semifirm, golden one that is an excellent melter. The soft one is used most often for cooking. Monterey Jack or muenster can be substituted. Anejo Cheese: Also known as Cotija, is a salty, crumbly white cheese, similar to feta in appearance. Romano or washed and dried feta are good substitutes. Panela Cheese: is a mild, milky-tasting, fresh white cheese often sold in rounds. A ricotta, farmers or dry cottage cheese can be substituted. The reason Mary Sue and Susan like to use one part manchego, one part panella and one-half part anejo is because they give a greater texture and flavor than just one cheese, but is not a hard-and-fast rule. They both say to go right ahead and use whatever you happen to have in the kitchen, or experiment and come up with you own cheese mix. Serves 6 as an appetizer, 3 as an entree. SOURCE: Mesa Mexican by Mary Sue Milliken and Susan Feniger with Helena Siegel.