In a large pan, over medium heat, add 1½ teaspoons olive oil and mushrooms. Sauté about 5 minutes, until golden. Remove mushrooms from pan and set aside.
Add the remaining 1½ teaspoons olive oil to pan and heat over medium-high heat. Add leeks, carrots, rutabaga, turnips and garlic and sauté 5 minutes. Stir in wine and continue to cook until liquid is reduced to ¼ cup, about 1 minute.
Add mushrooms, broth, chicken, thyme and pepper. Bring to a boil, reduce heat and simmer uncovered for about 15 minutes or until vegetables are tender.
Garnish with thyme springs.