1. Bring a large pot of salted water to boil. Cook penne according to package directions until al dente, about 13 to 14 minutes. Drain and rinse with cold water.
2. Meanwhile, in a large bowl, whisk together rice vinegar, soy sauce, miso, garlic, ginger, and honey until combined. Add olive oil and sesame oil and whisk until emulsified.
3. Add penne, chicken, cucumbers, and the white parts of the green onions to bowl and toss until everything is well coated with dressing. Taste and season with salt and pepper if needed. Top with sesame seeds and green parts of green onions. Serve immediately, or refrigerate for up to 2 days.