For the lobster sauce: In a medium saucepan over medium-high heat, reduce the white wine and tarragon vinegar with the peppercorns, shallots, bay leaf, tarragon and thyme until the mixture is nearly dry, about 10 minutes. Add the half-and-half and reduce by two-thirds, about 5 minutes.
Decrease the heat to low and whisk in the butter, chunk by chunk, stirring vigorously until each piece is nearly melted. Remove the lobster sauce from the heat and season it with lemon juice and salt. Strain the lobster sauce through a fine mesh chinois. Hold the lobster sauce warm in a saucepan over very low heat until the lobster meat is ready.
For the lobsters: Bring a large pot of salted water to the boil. Prepare a bath of icy water. Kill the lobsters by placing them on their backs on a cutting board and inserting a knife tip into their heads between the antennae. Drop the lobsters in the boiling water for 20 seconds and immediately shock them in the ice bath to stop the cooking. Extract the tail, claw and knuckle meat from the lobsters. The meat will still be translucent and raw. Remove the mud line from the tails and dice the tail meat into bite-size chunks.
Add the lobster meat to the lobster sauce. Very slowly warm the meat until it is just barely cooked through. Be sure to agitate the pan frequently to prevent the lobster sauce from breaking. If it does start to break, sprinkle it with a few drops of cold water and take it off the heat for a moment.
For the lobster rolls: In a saute pan, toast the sides of the buns with butter until crispy and golden. Spoon the cooked lobster meat into the prepared buns. Add as much lobster sauce as desired. Drizzle the lobster rolls with Mayo Mustard, drizzle with yogurt and sprinkle liberally with chives. Serve with lemon wedges.
Combine the dried mustard with 1 1/2 teaspoons water and lemon juice. Whisk in the mayo, Dijon, hot sauce and salt to taste.
Leftover lobster sauce can be used over baked potatoes or served with grilled or roasted fish.