Heat the oil over medium high heat until shimmering. Brown the cubed chicken. Sprinkle the browned chicken with 2 tablespoons of the taco seasoning mix. Stir in the water and 2 tablespoons of the sour cream.
Cook and stir until the chicken is no longer pink in center, scraping up the brown bits. Remove from the heat.
Mix the remaining sour cream, salsa, cheese, and remaining dry taco mix in a bowl and toss with the salad greens.
Spoon the chicken over a bed of mixed greens divided onto 4 plates and serve.