2 cups tightly packed fresh basil leaves
3 medium garlic cloves, peeled
6 green or red Thai chiles, stemmed [substitute 2 Serrano's or 1 medium jalapeno for Thai chiles]
2 tablespoons fish sauce
1 tablespoon oyster sauce
1 teaspoon white vinegar
1 tablespoon sugar
1 1/2 pounds boneless, skinless chicken breast, cut into 2-inch pieces
3 medium shallots, peeled and thinly sliced (about 3/4 cup)
2 tablespoons vegetable oil
Red pepper flakes to taste
Process 1 cup basil leaves, garlic, and chiles in food processor until finely chopped, 6 to 10 one-second pulses, scraping down bowl with rubber spatula once during processing.
Transfer 1 tablespoon basil mixture to small bowl and stir in 1 tablespoon fish sauce, oyster sauce, vinegar, and sugar; set aside.
Transfer remaining basil mixture to 12-inch heavy-bottomed nonstick skillet. Do not wash food processor bowl.
Pulse chicken and 1 tablespoon fish sauce in food processor until meat is chopped into -approximate 1/4-inch pieces, six to eight 1-second pulses. Transfer to medium bowl and refrigerate 15 minutes.
Stir shallots and oil into basil mixture in skillet.
Heat over medium-low heat (mixture should start to sizzle after about 11/2 minutes; if it doesn’t, adjust heat accordingly), stirring constantly, until garlic and shallots are golden brown, 5 to 8 minutes.
Add chicken, increase heat to medium, and cook, stirring and breaking up chicken with potato masher or rubber spatula, until only traces of pink remain, 2 to 4 minutes.
Add reserved basil-fish sauce mixture and continue to cook, stirring constantly until chicken is no longer pink, about 1 minute.
Stir in remaining cup basil leaves and cook, stirring constantly, until basil is wilted, 30 to 60 seconds.
Serve immediately with steamed rice and vegetables