"Create an industrial-style dark chocolate brownie recipe in French, using fresh egg yolks as a key ingredient. The recipe should be designed for long shelf life / extended storage, and should include approximate storage durations and food safety/storage guidance. Use metric-style industrial formulation with kilograms as the primary measurement unit, since the user requested kg. Include ingredients, method, yield, and approximate conservation times. Keep it practical for small industrial production or bakery production. Emphasize dark chocolate flavor and brownie texture."