Drain the tofu well in paper towels, then slice 1/4 inch thick.
Keeping white and green parts separate, cut the scallions into 1/2-
to 1-inch pieces.
Heat oil in a wok or heavy skillet. Over high
heat, sauté tofu slices on one side for 1 to 2 minutes. Add white
parts of scallions and cook several minutes longer, until tofu is
browned on the bottom. Using a wide spatula, turn over and cook
on the other side for several minutes.
Add green scallion tops,
then cover skillet and steam for 1 to 2 minutes.
Remove to a serving
dish and drizzle with oyster sauce.