1. In a small bowl, whisk together the soy sauce, chicken stock, sherry, sugar, ginger and wasabi; set aside.
2. Heat a large ovenproof skillet over medium-high heat. Add 1 tablespoon oil; swirl to coat. Add pork to pan; saute 4 minutes. Turn pork over; place pan in oven for 15 minutes or until a thermometer registers 145°F. Remove pork from pan; place on a cutting board. Let stand 5 minutes.
3. Being very careful. The handle on the pan will be HOT! Place pan back on the stove over medium heat. Pour in the soy sauce mixture and cook for about a minute. Stir in the scallions.
4. Cut the pork into thin slices. Divide onto plates and top with the sauce. Serve immediately.