This creamy chicken and asparagus pasta is a quick, warming meal all cooked in one pot. The cream cheese adds a silky texture to the sauce, while fresh asparagus and lemon brighten the dish.
Heat oil in a large high-sided skillet over medium-high heat. Add chicken in an even layer; cook, undisturbed, until browned on the bottom, about 4 minutes. Stir the chicken; cook, stirring occasionally, until no longer pink, about 2 minutes. Transfer to a plate.
Add leek, garlic and thyme to the pan; reduce heat to medium. Cover and cook, stirring occasionally, until the leek is softened, about 4 minutes. Return the chicken to the pan; stir in penne, broth and salt. Bring the mixture to a simmer over medium-high heat. Reduce heat to maintain a simmer; cook, stirring occasionally to prevent sticking, until the pasta is tender and the chicken is cooked through, 9 to 10 minutes, adding asparagus to the mixture during the final 5 minutes of cook time.
Remove from heat; stir in cream cheese, lemon zest and lemon juice. Sprinkle with chives and garnish with additional thyme, if desired. Serve immediately.