Possible Clues:

• Set askew around what's in the hold for a snail there
• Set out carrying consignment - one mollusc, from Paris
• Pricey hors d'oeuvre
• English southern -- principally cockney -- slang makes French scoff
• In France, slow mover set out carrying load
• Estimate including freight for a starter
• Food in shell is French, load being imported
• Key recherché slang for a French delicacy
• Mark tucking into eggs, initially came to one with shell
• Scare cook contracted to produce snail on the menu