Prepare rooibos iced tea: Boil the water and remove from heat. Steep the tea bags for 10 minutes. Sweeten with honey or sugar to taste. Let cool, then refrigerate until ready to serve over ice.

Preheat the oven: Preheat the oven to 275°F (140°C).

Cook chashu pork: In a Dutch oven, combine pork loin, soy sauce, sake, vinegar or mirin, sugar, scallions, garlic, ginger, shallot, and water. Submerge the pork in the liquid. Cover with a lid slightly ajar and cook in the oven for 1 hour.

Slice pork: Remove the pork and set aside. Strain the cooking liquid and reserve for the ramen broth and eggs. Once cooled slightly, thinly slice the pork.

Start ramen broth: Preheat a pot with vegetable oil over medium-low heat. Sauté onion, garlic, and ginger for 5 minutes.

Add vegetables and broth: Add mushrooms, leek, scallion whites, and broth. Ensure the vegetables are covered by about 2 inches of broth. Bring to a rolling boil, then reduce to a mild simmer and cover.

Reduce broth: Simmer until the broth reduces by half. Strain out and discard the solids using a fine-mesh sieve.

Optional eggs: If using eggs, gently lower them into the simmering broth and cook for 6 minutes. Transfer to an ice bath for a few minutes, then peel and set aside.

Cook noodles: Add ramen noodles to the simmering broth and cook according to package directions.

Finish and serve: If using eggs, slice each in half and place two halves in each bowl. Serve hot with chilled rooibos iced tea.