Cook the potatoes until done. Then peel and slice them. Souse with vinegar, oil and some stock. Add an onion cut into small pieces and mingle everything carefully before letting it pervade. Prior to serving season with salt and pepper and mingle once again carefully.
Check the tenderloin for fishbones and season with salt, pepper, lime juice and herb butter. Wrap into aluminum foil and cook in the oven.
Cook the sepias in a stock made garlic, onions and white wine for 30 minutes.
Decorate the potato salad with the fish and the sepias on a plate. Grate some carrots over the potato salad.