Heat a wok or medium skillet over medium-high heat. Add the oil and
swirl to coat the surface. When the oil is very hot but not smoking,
add the shrimp and stir-fry until they begin to color on all sides,
about 1 minute. Add the pesto and stir-fry until it coats the shrimp
and begins to cook, about 1 minute. Add the fish sauce and toss the
shrimp for another 15 seconds to mix it in. Transfer the shrimp and
sauce to a serving platter. Sprinkle with cilantro leaves and serve.
