While sweet potato is cooking, in a large nonstick skillet, heat 1 tablespoon olive oil. Rinse salmon steaks, pat dry, and season with tamari. Place salmon in skillet and brown for about 4 minutes on each side, or until just opaque throughout. In a second skillet or wok, heat remaining 1 tablespoon olive oil. Add bok choy and toss to coat; cover and cook over medium heat until bright green, about 5 minutes. Sprinkle with balsamic vinegar.