Heat 1 tablespoon oil in a large nonstick skillet coated with cooking spray over medium-high heat. Add basil, garlic, and mushrooms; cook 5 minutes, stirring frequently.
Combine chicken broth and cornstarch in a small bowl. Add broth mixture and Marsala to mushroom mixture. Bring to a boil; cook 1 minute, stirring constantly. Reduce heat to medium-low; cook 5 minutes, stirring frequently.
While sauce cooks, combine salt, garlic powder, and pepper; sprinkle over turkey. Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add turkey; cook 2 minutes on each side or until done. Serve with sauce. Garnish with basil sprigs, if desired.