In a large bowl combine 2 Tbsp soy sauce, lemon juice, ginger and garlic. Add cubed turkey and marinate for 15-30 minutes in refrigerator.
Using a slotted spoon remove turkey from marinade to a clean bowl. Discard marinade. Sprinkle turkey with ¼ cup of cornstarch and toss to coat.
In a large fry pan heat oil over medium-high heat. Working in 2 batches, add turkey cubes and sauté, turning, until cooked through. About 4 minutes per batch. Set aside on a paper towel.
Drain mandarin oranges , reserving liquid (about 2/3 cup). Set aside.
In a saucepan over medium heat, add remaining 1 Tbsp soy sauce, honey, reserved orange juice, marmalade, rice vinegar and sesame oil. In a small bowl mix remaining 1 Tbsp cornstarch with 2 Tbsp water to make a slurry. Stir into sauce. Bring a low boil stirring, until sauce thickens.
Add turkey cubes to sauce and toss to coat. Add mandarin oranges and cashews, stirring to combine.
Serve over rice with steamed broccoli or salad on the side.