Score the fat of the duck breast in a cross-hatch pattern with a sharp knife. In a small bowl whisk to combine the salt and five-spice powder. Work the spice mix into the duck breast and set aside to dry brine for 1 hour at room temperature.
While the duck is resting, place the bamboo shoots and shiitakes in a skillet. Add the soy sauce, mirin, and sugar and stir to combine. Bring the mixture to a boil and reduce to a simmer. Place a cover on the skillet and let cook for 15 minutes. Transfer the mushrooms and bamboo shoots to a bowl and set aside.
Wipe out the skillet and place the duck, skin-side-down, in the center. Place over low heat and cook for 10 minutes undisturbed. Once the 10 minutes have passed, carefully pour off all but 2 tbsp of the duck fat. Flip the breast and cook for 10 minutes more. Transfer the duck to a cutting board and let rest for 10 minutes before slicing. Cook the corn in the same pan the duck was cooked in until tender. Transfer to a bowl and set aside.
Pour the stock in a large pot and place over medium heat. While reheating the stock, place a pot of water over high heat and place a steaming basket on top. Add the yu choy to the basket and bring the water to a boil.
Once the water is boiling and yu choy is tender, remove the steaming basket and set aside. Add a bundle of noodles to the water and cook until tender, about 3 minutes. Drain the noodles well. For the sake of portioning the noodles correctly, I recommend cooking the noodles a bundle at a time. To save the boiling water, simply fish the noodles out of the water using a spider or large slotted spoon before transferring to a fine mesh strainer to shake out any excess moisture.
To assemble the bowl, pour 2-3 tablespoons of the tare into the bottom of a large bowl. Add a bundle of cooked noodles and ladle hot stock over top. Top the soup bowl with 3-4 slices of duck, half a ramen egg, a few pieces of steamed yu choy, a generous spoonful of braised bamboo shoots and shiitakes, a spoonful of corn, and a sprinkling of scallions, squash blossoms, and sesame seeds. Serve immediately with cold beer.