Galician Lobster and Watercress Salad

In a large pot, bring the clam juice and water to a boil over high heat.
Carefully add the live lobsters headfirst into the boiling liquid.
Cover the pot and boil for 15 minutes or until the lobster shells are bright red and their tails are curled.
Remove the lobsters from the pot, transfer them to a platter, and let them cool.
Once cooled, remove the shells from the tails and claws, and cut the tail into ½-inch-thick slices.
Cut the remaining lobster meat into large chunks.
Optionally, reserve the red coral (eggs) if desired.
In a medium saucepan, place the potatoes and turnips with cold water to cover, and add salt.
Cover the saucepan and bring to a simmer over low heat.
Cook for about 20 minutes or until the potatoes and turnips are tender when pierced with a knife.
Drain and let them cool slightly before peeling and cutting them into ½-inch slices.
Finely chop enough watercress to make 3 tablespoons.
In a mortar or mini-processor, mash the garlic, peppercorns, watercress, mint, and ⅛ teaspoon salt.
Stir in the Dijon mustard and lemon juice, then transfer the mixture to a small bowl.
Add the olive oil and whisk until well combined.
Adjust the seasoning to taste.
Arrange the remaining watercress on a serving platter.
Scatter the thinly sliced radishes over the watercress and season with salt.
Place the lobster meat in the center of the platter.
Arrange the sliced potatoes and turnips around the edge.
Finally, pour the dressing over the salad and serve immediately.