1. Whisk together water, orange juice, sherry, miso, salt, and pepper in a medium bowl until smooth. Add prunes and rosemary and set aside.
2. Place flour in a shallow dish. Dredge turkey lightly in the flour, shaking off excess.
3. Heat 2 teaspoons oil in a medium skillet over medium-high heat. Add the turkey and cook until golden (2 minutes per side). Transfer to a plate and cover with foil to keep warm.
4. Heat the remaining 2 teaspoons oil in the pan over medium heat. Add shallot and mushrooms; cook, stirring, until browned (3-5 minutes). Add the miso mixture and cook, stirring, until slightly thickened (2-3 minutes).
5. Reduce heat to low and return the turkey and any accumulated juices to the pan. Simmer gently, spooning sauce over turkey, until heated through (1-2 minutes).