In a large skillet over high heat, heat oil until hot. Add white and shiitake mushrooms, red bell pepper and garlic; cook, stirring occasionally, until mushroom liquid has nearly evaporated, about 6 minutes. Add wine and boullion cube; cook, stirring occasionally, until wine is slightly reduced and boullion cube dissolves, about 4 minutes.

Meanwhile, in a cup combine cornstarch and 1 cup water until smooth. Add to skillet, along with green onions, basil, oyster sauce and ground red pepper.

Bring to a boil, stirring constantly until lightly thickened and clear; about 1 minute.