Peggy Trowbridge Filippone is a writer who develops approachable recipes for home cooks. Her recipes range from Grandma’s favorites to crab boil sauce latest food trends. 2,000 calories a day is used for general nutrition advice. Nutrition information is calculated using an ingredient database and should be considered an estimate.

Add the butter and oil to a medium, heavy stockpot over medium-high heat. Once the butter has melted, add the onion, celery, and carrots and then cook until soft, about 4 minutes. Stir in the flour and continue to stir until the mixture is a light blond color, about 2 minutes. Add the cognac and stir for 30 seconds, scraping the bottom of the pot with a wooden spoon to release any browned bits.

Add the lobster shells, then stir in the shrimp stock. Bring to a boil over high heat. Reduce the heat to medium-low and add the tomato paste, salt, paprika, and cayenne. Remove the shells and strain the sauce through a fine-mesh strainer into a medium saucepan. Add the heavy cream and bring to a boil over medium-high heat.

Reduce the heat to medium and simmer briskly until the sauce is reduced to about 3 cups, about 15 minutes. Use warm with seafood dishes or as a finishing sauce. Lobster shells are rich in flavor and can be used in all kinds of dishes, such as lobster stock for soup, chowder, or risotto. The same method may be used with crab or shrimp shells. Thaw in the refrigerator and then continue with the recipe.