Shiitake Mushrooms with Scallions

1 tablespoon peanut oil
1/4 lb sliced bacon, cut crosswise into 2 1/2-inch pieces
12 scallions (white and pale green parts only), crushed with side of a heavy knife and coarsely chopped
4 large garlic cloves, thinly sliced
2 cups chicken broth (16 fl oz)
1/2 teaspoon salt
1/4 teaspoon white pepper
1 lb fresh shiitake mushrooms, stems discarded

Heat a wok or 12-inch heavy skillet over high heat until a bead of water dropped onto cooking surface evaporates immediately. Add oil, swirling it around wok, and heat until it begins to smoke. Add bacon and stir-fry until brown and crisp, about 3 minutes. Transfer with a slotted spoon to paper towels to drain and reserve for another use.

Add scallions and garlic to bacon fat and stir-fry until fragrant, about 1 minute. Pour broth down side of wok (it will bubble vigorously), add salt and white pepper, and bring to a boil. Add mushrooms, then reduce heat and simmer, uncovered, turning occasionally, until tender, about 5 minutes.

Transfer mushrooms to a bowl with a slotted spoon and, when cool enough to handle, cut into 1/4-inch-thick slices. Drizzle liquid over mushrooms if desired.