Bring chicken broth to simmer in medium saucepan. Reduce heat to low; cover and keep broth hot.
Melt 3 tbsp butter with olive oil in heavy large saucepan over medium heat. Add chopped shallots; sauté 1 minute. Add wild mushrooms; cook until mushrooms are tender and juices are released, about 8 minutes. Add rice and stir to coat. Add sherry and simmer until liquid is absorbed, stirring frequently, about 8 minutes. Increase heat to medium-high. Add 3/4 cup hot chicken broth and simmer until absorbed, stirring frequently. Add remaining hot chicken broth 3/4 cup at a time, allowing broth to be absorbed before adding more and stirring frequently until rice is just tender and mixture is creamy, about 20 minutes. Stir in Parmesan cheese and chopped fresh thyme. Serve warm.