For the marinade: Combine the meat, oyster sauce, sesame oil, soy sauce and sugar in a big mixing bowl until all the meat is coated. Marinate in the fridge for about 30 minutes.
For the onions: Combine 3 cups water, the vinegar and sugar in a small pot and bring to a boil. Place the red onions in a large bowl. Once the pickling liquid boils, pour it over the red onions and chill in the fridge for 30 minutes.
For the mayo: Beat the yolks in a food processor. Slowly add the oil 1 tablespoon at a time until the yolks thicken. Add the salt and garlic. Let the processor continue mixing the egg yolks and oil until it reaches the consistency of mayo.
For cooking: Heat a wok to medium-high heat and add the oil. As it gets hot, add the cubed beef and toss until it has reached your preferred level of doneness. We suggest medium-rare.
Slice open the French baguette and spread the Vietnamese mayo over. Layer on the watercress, filet mignon, pickled red onions and grilled jalapenos. Finally, squeeze preferred amount of lime juice on top and add salt and pepper to taste.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.