Butterfly and broil lobster tail. For the sauce: Combine all of the ingredients and bring to a boil until tickened. Remove from heat and rest. In a small sauce pan, melt the butter and add the lemon juice. Place the lobster tail in the butter and coat completely. Using a 1.5 inch tall cylinder mold, create a column of mashed potatoes, ladle the bisque around it. Top with the butter-broiled lobster tail and garnish with celery strings.