Soak the vegetarian beef in water mixed with a little vinegar for about 30 minutes. Squeeze out the water and rinse several times. Finely chop about 3 stalks of lemongrass and marinate with bouillon powder for about 1 hour to let the flavors absorb.

Peel the daikon and carrots. Save the middle sections to cut into flower shapes if desired; cut the rest into chunks for the broth. Peel and core the apples. Trim the lemongrass, keeping only the bottom 6 inches. Add 12 cups water (about 3 liters) to a pot, then add 3 tablespoons vegetarian fermented bean paste, the prepared vegetables, and lemongrass. Simmer on the stove for 1 hour. Strain the broth and discard the solids to get a clear soup base.

Heat vegetable oil in a pan and add annatto oil for color. Add more oil if needed and stir-fry the marinated vegetarian beef until well flavored. Slice the flower-shaped carrots and daikon into 1/2-inch thick pieces. Lightly crush the remaining lemongrass. Add everything to the broth and bring to a boil. Season with 1 tablespoon brown sugar, 1/2 tablespoon salt, and bouillon powder to taste. Adjust seasoning as needed, then add annatto oil for a vibrant color.

Blanch the noodles and drain well. Place noodles in a bowl, top with vegetarian sausage, beef, carrots, and daikon. Ladle hot broth over the top and garnish with cilantro for a complete bowl of vegetarian bún bò.