Peel off the muscle on the side of the scallop and discard. Slice in half, crosswise to make 2 round pieces from each scallop. Season with salt and pepper. Heat a large saute pan over medium-high heat. When the pan is hot, add the oil and sear the scallops for 15 to 30 seconds on each side. Remove from the pan and set aside. Pour any excess oil out of the pan and discard. Carefully deglaze with sake while the pan is off the heat. Return the pan to the heat. Add the soy sauce, ginger, garlic, honey, and barbecue sauce. Bring to a boil, lower to a simmer, and cook until thickened. Add the scallops back to the pan and toss to coat and heat through. Remove from the heat and add the green onions. Serve immediately over wasabi mashed potatoes.;
Cut the potatoes into large pieces of equal size. Put in a medium-size pot and cover with salted water. Bring to a boil and cook until tender. Drain thoroughly. Pass through a food mill and whip in the butter, hot cream and roasted garlic puree.
Blanch the spinach in boiling salted water for 10 seconds. Refresh in ice water. Drain thoroughly. Transfer to a blender and add wasabi powder. Process to a puree. Stir into warm mashed potatoes. Season with salt and pepper, to taste.