Heat the Olive Oil (1 tablespoon) and Butter (1 tablespoon) in a large stockpot or dutch oven with at least 5-quart capacity over medium heat. Add the Carrot (3 cup), and Celery (2 cup) along with the Salt (1 teaspoon) and Freshly Ground Black Pepper (1/2 teaspoon). Cover and sauté for 5 minutes.
Add the Leek (2 cup) and Fresh Parsley (1/4 cup). Stir to combine. Cover and continue cooking for an additional 10 minutes.
Remove the cover and increase the heat to medium-high. Add the Chicken Broth (2 can) along with the Fresh Dill (1/4 cup). Mix well and bring to a boil.
Reduce heat to medium and add the Orzo Pasta (1 cup). Simmer until pasta is cooked to al dente according to package directions, around 7 minutes.
When the orzo is just about done, add the Rotisserie Chicken (2 cup), stir to combine and continue simmering until just heated through, 1 to 2 minutes.
Serve immediately in bowls, sprinkled with additional fresh dill if desired.