How to Make It
In a large skillet, cook the bacon and ginger over moderately high heat, turning the bacon once, until lightly browned, about 5 minutes. Spoon off all of the fat in the skillet. Add the chicken broth, mirin, vinegar, sugar and soy sauce to the skillet and simmer over very low heat, turning the bacon occasionally, until it is tender and the liquid is reduced to a syrupy glaze, about 10 minutes. Cover and keep warm.
Meanwhile, fill a roasting pan with 2 inches of water and set 4 ramekins in the corners of the pan. Line a 9-by-13-inch baking pan with parchment paper and spray with vegetable oil spray. Arrange the biscuits in the baking pan and set it on top of the ramekins in the roasting pan, over the water. Cover the roasting pan very tightly with foil and bring to a boil over high heat. Steam the biscuits until fluffy and cooked through, about 8 minutes.
Carefully split each biscuit with your fingers and arrange them on a platter; spread the bottoms with hoisin sauce and Sriracha and top with the glazed bacon. Drizzle each bun with some of the glaze and garnish with sliced scallions, radishes and pickles. Close the buns and serve right away.