Cut the pho noodles into strips and gently separate them. Toss with a little oyster sauce and soy sauce. Slice the beef and marinate with a bit of vegetable oil and seasoning powder. Add black pepper. Mince garlic and slice shallots.

Cut the tomato into wedges. Cut celery and leeks into 2-inch (about 5 cm) pieces. Thinly slice the onion. Adjust the amount of vegetables to your preference. Mix about 2 teaspoons cornstarch with half a small bowl of water and a little seasoning powder until dissolved.

Heat a pan over medium heat and add vegetable oil. Sauté the shallots until fragrant, then add the pho noodles. Stir-fry gently for about 5 minutes, being careful not to break the noodles. Transfer the noodles to a plate. Add the vegetables to the pan with a little seasoning powder and oyster sauce. Stir-fry until just cooked, then place on top of the noodles.

Add oil to the pan and sauté the minced garlic until fragrant. Add the beef and stir-fry quickly. When almost cooked, pour in the cornstarch mixture and stir quickly. Place the beef on top of the noodles. Sprinkle with black pepper and serve hot.