Moist sautéed chicken is the key to a dish's success. Little chunks of skinless chicken breast love to stick to the pan, so it's important that the pan and the oil are good and hot before you add the chicken. Even then, the chicken will stick—but it will also begin to brown. That's good. This way you're sure to get little caramelized nubs (the French call this delicious brown stuff fond) that will ultimately dissolve into the pan sauce, giving it a savory richness.
Don't use a nonstick pan, but do let the chicken sit undisturbed in the pan for about a minute. Once the chicken pieces take on a golden-brown crust, shimmy the straight edge of a metal spatula under them to loosen and flip them without tearing.
Since the chicken is cut into 3/4-inch pieces, it takes just a few minutes to finish cooking. It's important not to let the chicken overcook, as it would dry out and become chewy. To check for doneness, I just cut a good-size piece in half. The chicken should still be faintly pink in the center—mere moments from being cooked through—when it gets pulled from the pan. The chicken will actually continue to cook through from its residual heat.