For the mashed turnips: Cut off the stems and leaves from the turnips. Set aside. Scrub the turnips under running water. Cube the turnips. Put turnips and 1 garlic clove into a pot and cover with water. Add salt and bring water to a boil. Boil for 25-30 minutes or until tender. Drain. Add turnips and milk, cream, or butter to a bowl. Mash the turnips and garlic. Add salt and pepper to taste. Set aside.
For the turnip green pesto: Bring large pot of water to a boil. Add leaves and stems (the greens) and cook for 1 minute. Remove greens to colander. Put drained greens into a food processor with 1 garlic clove, toasted walnuts, salt and pepper. Process 2 minutes. While processor running, add lemon juice and 2-3 TBSP olive oil (depending on desired consistency). Process until smooth. Add cheese. Pulse a few times. Remove.
To assemble, spread mashed turnips onto crostini and top with a dab of turnip green pesto.
**Can buy crostini or cut French baguette into thin slices, rub slices with olive oil. Bake on cookie sheet 350 degrees for 15-20 minutes, turning once.