In a large pot, heat olive oil over medium-high heat until it glistens, then add leeks and sauté until they soften, 3-4 minutes. Add the parsnips, rutabaga, chicken broth, white wine, and bay leaf and bring to a boil. Lower the heat and simmer until the vegetables are tender, about 25 minutes. Add the mussels, cover, and steam until the shells open—this should take only a few minutes. (Discard any mussels with broken shells or ones that do not open.) Transfer the mussels to a serving dish and cover to keep warm.