Split large carrots in half lengthwise. Quarter parsnips lengthwise. In a Dutch oven bring salted water to boiling. Add carrots and parsnips and simmer 5 minutes; drain.
In a very large skillet, heat oil over medium heat. Add garlic and cook 30 seconds or until fragrant and beginning to brown. Add carrots, parsnips, and cipollini onions to skillet. Cook and stir for 5 minutes or until coated in oil and beginning to soften. Sprinkle with salt and pepper.