1. Melt butter in a large nonstick skillet over medium heat. Add leek to pan; cook 2 minutes or until tender, stirring occasionally. Add mushrooms; cook 7 minutes or until moisture evaporates, stirring occasionally. Stir in parsley, sherry, sage, 1/8 teaspoon salt, and 1/8 teaspoon pepper; cook 1 minute.
2. Combine 2 cups water, bay leaves, and broth in a medium saucepan; bring to a boil. Gradually add polenta to pan, stirring constantly with a whisk. Reduce heat, and simmer 5 minutes or until thick, stirring frequently with a whisk. Remove from heat; discard bay leaves. Stir in remaining 1/8 teaspoon salt, remaining 1/8 teaspoon pepper, and shredded cheese. Spoon 2/3 cup polenta onto each of 6 plates; top each serving with 1/2 cup mushroom mixture and 1 teaspoon shaved cheese.