Rinse shrimp under cold water.

Peel them and place peeled shrimp in a bowl, reserving peels separately.

Chill peeled shrimp.

Heat 1 tablespoon oil in a large pot.

Add shrimp peels and cook, stirring occasionally, until fragrant and red in color, about 5 minutes.

Add vermouth and cook until the bottom of the pan is almost dry, about 3 minutes, stirring occasionally.

Add white wine and cook for another 3 minutes, stirring.

Add fish stock, 2 cups water, carrots, celery, shallot, bay leaf, tarragon, 1 sprig parsley, tomato paste, peppercorns, vanilla bean seeds and pod.

Bring to a boil, reduce heat to a low simmer and cook for about 45 minutes, uncovered.

Strain sauce into a large bowl, pressing the peels with a wooden spoon to yield as much liquid as possible.

You should have about 2 cups liquid.

Set aside while you cook the shrimp.

Devein shrimp, rinse under cold water, and drain thoroughly.

Heat remaining tablespoon oil in a skillet.

Add shrimp and cook over high heat, until just pink.

Cook in batches as needed to avoid overcrowding the pan.

Keep warm while you finish the sauce.

Add the liquid to the pan used for cooking the shrimp and bring to a simmer once more.

Taste and adjust seasoning with salt and pepper.

Take from the heat and add butter, whisking constantly until it melts.

Add shrimp to the sauce just to reheat.

Chop leaves from remaining sprig of parsley and serve immediately.