Upon completing his traineeship in Neuwied and after a first employment in Mainz – then ruled by the French – Kessler joined the champagne house Veuve Clicquot-Ponsardin in Reims, France, as a ‘commis‘ (commercial clerk). Due to Napoleon’s Continental Blockade, Great Britain had been lost as an important market, precipitating his employer in financial and economic predicament. Kessler, who was capable of opening up new sales channels for the company, advanced rapidly within the firm. After just three years he was promoted and received power of attorney from his employer, the widow Barbe-Nicole Clicquot (‘Veuve Clicquot‘).