Combine soy sauce, lemon juice, mirin, 2 tablespoons water and bonito in small bowl. Let stand 30 minutes. Strain sauce through fine strainer; discard bonito shavings. (Can be made 4 hours ahead. Cover and let stand at room temperature.)
This easy, one-skillet chicken stroganoff features tender chicken breasts, savory mushrooms, and a creamy Dijon-crème fraîche sauce—perfect for weeknights.