Hebridean langoustine bisque

Method

Humanely chill langoustines, then quickly destroy the nerve ganglion; separate heads and shells from tails, reserving tails for garnish. Heat butter in a heavy-bottomed pan over medium heat and sweat shallots, celery and fennel until soft without colouring, approximately 5 minutes. Add langoustine heads and shells, stirring constantly for 3-4 minutes to gently toast and release flavours. Stir in tomato paste, cook for 1 minute, then deglaze with Fino sherry, scraping the pan base; reduce by half. Add cold fish stock, bring to a gentle simmer and cook for 25 minutes, skimming occasionally. Strain through fine chinois into a clean pan, pressing gently on solids to extract essence without bitterness. Whisk in cream and milk, season to taste with salt and white pepper, then finish with cognac and fresh tarragon. Pour into warm bowls, garnish each with a gently warmed langoustine tail and micro herbs, finish with a turn of cold butter for richness and gloss.