Slice bean curd into 1/4" cubes; sliver green onions. In hot wok, heat oil just to point of smoking.
Add bean curd, green onions and garlic. Stir gently to avoid breaking up curd; turn pieces to coat with oil. Be sure oil is not too hot or curd will tend to stick to pan.
When aroma of garlic is apparent, add stock and bring to boil. Lower heat, cover, and simmer for about 30 seconds (don't let curd fall apart). Remove cover; stir in oyster sauce and sugar.
Increase heat, and when liquid boils again, add enough cornstarch paste to make a creamy (but not too thick) sauce.
Swirl in peanut oil to make a glaze. Serve over rice or in a shallow serving bowl.