How to Make It
In a large bowl, cover the shiitake with water and let soak overnight at room temperature. Drain the mushrooms and discard the stems.
In a large saucepan, heat 2 tablespoons of the oil until shimmering. Add the smashed ginger, sugar and scallion and cook over moderate heat, stirring, until the sugar dissolves and starts to caramelize, 4 to 5 minutes. Add the mushrooms and the 2 cups of chicken stock and bring to a boil. Cover partially and simmer over low heat, stirring occasionally, until the mushrooms are tender and most of the stock has evaporated, 1 hour and 15 minutes. Stir in the 1 tablespoon of oyster sauce and season the braised mushrooms with salt.
Meanwhile, in a small saucepan, heat the remaining 1 tablespoon of canola oil until shimmering. Add the ginger matchsticks and cook over moderately high heat, stirring, until lightly golden, 1 minute. Add the whiskey and cook for 30 seconds. Add the remaining 2 tablespoons of chicken stock and 1/4 cup of oyster sauce and simmer over moderately low heat until thickened, about 5 minutes. Keep the ginger oyster sauce warm.
In a large pot of salted boiling water, blanch the bok choy until crisp-tender, 2 minutes. Drain and cool under running water; pat dry.
Light a grill or preheat a grill pan. Brush the bok choy with oil and grill over high heat, turning, until lightly charred, 5 minutes. Transfer to plates or a platter and top with the mushrooms. Drizzle the ginger-oyster sauce over the bok choy and mushrooms and serve.