Heat oil in Dutch oven or stockpot over medium-high heat; brown steaks about 2 minutes per side. Add 1-1/2 cups (375 mL) water, sake, soy sauce, sugar, onions, garlic, cinnamon sticks and ginger root.

Simmer, covered, on stove-top or in a 325°F (160°C) oven for 1-1/4 hours or until fork-tender. Remove cinnamon sticks and ginger; discard. Remove steak and set aside.

Mix cornstarch with 1 tbsp (15 mL) cold water until smooth. On stove top, heat sauce over medium heat and gradually stir in cornstarch mixture; bring to boil and heat for 1 to 2 minutes, until thickened. Return steak to pan. Stir in spinach; cook for 3 minutes or until wilted.

Slow Cooker Option: Can be made in a slow cooker; combine all ingredients except cornstarch and spinach and cook covered for 5 hours on HIGH or 8 hours on LOW until meat is fork-tender. Thicken sauce on stove-top as above. Add spinach and cook for 3 minutes or until wilted.