How to Make It
In a small saucepan, melt the butter. Whisk in the miso, Sriracha and lemon juice. Reserve 1/4 cup of the miso-chile butter for serving.
Light a grill. In a large bowl, toss the scallions with the oil and season with salt and pepper. Grill over moderate heat, turning, until lightly charred and tender, 5 minutes. Chop the scallions and toss with 1 tablespoon of the miso-chile butter.
Skewer the lobster bodies from the tail to the head to keep them straight. Brush the lobster meat with 2 tablespoons of the miso-chile butter. Grill the lobster bodies and claws over moderate heat, turning and basting the meat with the remaining miso-chile butter, until the shells are bright red, 7 to 8 minutes for the tails and 12 to 15 minutes for the claws. Remove the skewers.
Arrange the lobsters on a platter or plates and scatter the scallions on top. Serve with lemon wedges and the reserved 1/4 cup of miso-chile butter.