In a medium bowl, stir together the butter, cilantro, garlic, shallot, 2 tablespoons of lime juice, and sriracha sauce. Spoon onto waxed paper and roll into a log. Place into the freezer until set.

Preheat a grill for high heat.

Place whole oysters on the hot grill for 3 to 5 minutes, or until almost done. Remove the top shell from the oysters, without spilling any liqueur, and return them to the grill. Slice the butter log into 1/4 inch slices, and place a slice on top of each oyster. Grill until the butter melts, then serve on a bed of rock salt for presentation.