Place 1 1/2 cups boiling water and porcini in a bowl. Cover and let stand 30 minutes or until tender. Drain through a sieve over a bowl, reserving soaking liquid. Finely chop porcini; set aside.
Melt butter in a large nonstick skillet over medium-high heat. Add shallots, and sauté 3 minutes. Add cremini; sauté 3 minutes. Sprinkle cremini mixture with 1/4 teaspoon salt and 1/8 teaspoon pepper. Add wine, and cook 1 minute or until liquid evaporates. Remove from heat; stir in 1/4 cup porcini and thyme.
Cut a horizontal slit through the thickest portion of each tenderloin to form a pocket. Fill the pockets evenly with cremini mixture, and secure at 1-inch intervals with twine. Sprinkle tenderloins with 1/4 teaspoon salt and 1/8 teaspoon pepper. Dredge tenderloins in 1 1/2 teaspoons flour.
Heat the oil in a large nonstick skillet over medium-high heat. Add turkey; cook 4 minutes on each side or until browned. Add the reserved soaking mixture and broth, and bring to a boil. Cover, reduce heat, and simmer 8 minutes. Remove turkey; keep warm. Cook broth mixture until reduced to 3/4 cup (about 5 minutes). Combine 1 tablespoon flour and milk, stirring with a whisk. Add milk mixture to broth mixture; bring to a boil. Reduce heat, and simmer 2 minutes. Stir in 1/4 teaspoon salt and remaining porcini.
Remove twine from tenderloins; slice turkey diagonally. Serve with sauce.