Cook pasta, drain well. Set aside, and keep warm.

Cook mushrooms and garlic in oil in a large skillet over medium-high heat, stirring constantly, until tender. Remove mushrooms and garlic, reserving oil in skillet; set vegetables aside, and keep warm.

Dredge chicken in flour; brown chicken in oil in skillet over medium heat. Remove chicken, reserving drippings in skillet; set chicken aside, and keep warm. Add artichoke hearts to drippings; cook over medium-high heat, stirring constantly, until golden.

Remove artichoke hearts, reserving drippings in skillet; set artichokes aside, and keep warm.

Add vermouth to drippings in skillet; cook over high heat, deglazing pan by scraping particles that cling to bottom. Add chicken broth and lemon juice, and simmer 1 minute. Add mushrooms, garlic, chicken and artichoke hearts. Add heavy cream and Parmesan cheese; bring just to a boil. Reduce heat, and simmer 5-7 minutes, stirring constantly. Place pasta on a large serving platter, and top with chicken mixture. Sprinkle with tarragon, and serve immediately.