Step 1

Puree all sauce ingredients except oil with 1 1/4 teaspoons salt in a blender until smooth, then strain through a mesh sieve into a bowl, pressing on solids, then discarding them.

Step 2

Heat oil in a deep heavy large skillet over medium heat until it shimmers.

Step 3

Carefully pour in sauce and simmer gently, stirring occasionally, for about 10 minutes. (Sauce will still be thin).

Step 4

Taste, and season with pepper, and more salt, if desired.

Step 5

Set aside, but keep warm over low heat.

Step 6

Roast chilis on their sides over a gas flame over medium-heat, turning with tongs, until skins are blistered and slightly charred, 4 - 6 minutes. (Or, broil on a rack about 2 inches from heat).

Step 7

Transfer to a large bowl and cover with plastic wrap, let stand for 20 minutes. (This can be done ahead of time).

Step 8

Carefully rub off skins from chilies, leaving stems attached.

Step 9

Cut a slit lengthwise in each chile using kitchen shears or a sharp knife.

Step 10

Carefully cut out ribs and the seedpod. Clean out all seeds with a wet paper towel, if necessary (Leaving the seeds will make the peppers more hot).

Step 11

Stuff chilies with cheese and enclose filling by overlapping slit slightly, then transfer to a plate. (All this can be done the day before).

Step 12

Heat 1/2-inch of oil in another large heavy skillet over medium heat until it registers 350° F on thermometer.

Step 13

While oil heats, beat egg whites with 1/2 teaspoon salt, using an electric mixer until they just hold stiff peaks.

Step 14

Whisk in the yolks, two at a time, just until incorporated.  Next, whisk in 1/4 cup flour.

Step 15

Spread 1 cup of flour onto a plate. Generously dust chilies with the flour, coating all sides. Gently shake off excess flour.

Step 16

When oil is ready, dip chilies, 1 at a time into egg batter, spooning it over chile to cover completely.

Step 17

Fry the chilis, turning once, until golden on all sides (Lap oil over any lighter areas, 4 to 5 minutes).

Step 18

Transfer chilies with a slotted spoon to paper towels to drain.

Step 19

Meanwhile, re-heat sauce.

Step 20

Ladle sauce onto plates and place a chili on top of sauce.