Prawn heads to add flavor in bisques..........?!

yes they give lots of flavor, the shells do as well, just caramelize them with a mirepoix and white wine, spices and water, cook down slowly and you will have a rich shrimp or seafood stock or sauce what ever you want.

you can use lobster shells, tails, fish bones(preferably white fish) anything like that will enhance flavor.

also its nice to add tomato paste or tomato product for the acidity.

good luck

im a chef

Shrimp shells will give a less-intense flavor that would come from shrimp heads but most people aren't using shrimp heads in their kitchen.

Shells from shrimp can be saved air-tight in the freezer if they aren't going to flavor stock right away.

Absolutely shells and heads I make this once a week at my restaurant we use lobster bodys

Other than the prawn head, add some onions.