For the Yams: Place a sheet of aluminum foil on the bottom oven rack, then preheat oven to 400 degrees F.
Bake yams on the top rack for 1 1/2 hours, or until they are soft and have started to ooze beads of dark syrup. Remove yams from oven and allow to cool slightly. Then separate and discard the skins. Whip yams in a food processor or mash by hand. (Unlike regular mashed potatoes, yams benefit from the smoothness created by a food processor.) Add nutmeg and slowly mix in half-and-half. Reserve.
For the Spinach: Remove stems, then wash spinach thoroughly. Shake off excess water, but do not dry.
In a non-aluminum pot, over medium heat, add the oil, garlic, and leek. Stir until leeks and garlic become translucent. Add spinach and cover pot. Cook for approximately 5 minutes, or until spinach has completely wilted. Let cool, then squeeze out all liquids. Puree spinach in a food processor along with salt, pepper and nutmeg. Reserve.
For the Beets: Preheat the oven to 450 degrees F.
Roast beets in the oven until tender, about 1 1/2 hours. Let cool. Peel off skin and discard. Then puree beets in a food processor. Reserve.
For the Scallops: Season the scallops with salt and pepper. Saute in a butter over medium-high heat for approximately 2 minutes per side, or until cooked throughout.
Reheat vegetables just before serving. Spoon 1 dollop of veggies onto each palette, and add 1 scallop. Serve immediately.