Prepare the ingredients as listed above.
Add all the ingredients for the chashu pork to a bowl, then submerge the pork into the liquid. Cover with a lid. Marinate for at least 1 hour in the refrigerator.
Strain the liquid and reserve for the ramen and eggs, remove the pork.
Make the mayu: Add garlic and canola oil to a pot, then simmer over low heat for 10 minutes, constantly stirring until blackened.
Transfer into a blender, add sesame oil, then whiz for approximately 30 seconds, so the garlic completely disintegrates. (Store in a sealed container in the refrigerator for up to two months).
Make the broth: Preheat an oiled pot to medium-low heat. Saute the onion, the garlic, and the ginger for 5 minutes, stirring often.
Add the mushrooms, the leeks, the scallions, and the reserved broth into a pot, so the vegetables are fully covered. Add more broth if needed.
Cook over high heat until the water reaches a rolling boil.Lower the heat to a mild simmer, then cover the pot with a lid. Cook until it reduces by 1/4 to enhance the flavor.
Place the eggs into the broth, lower the heat to a simmer, and cook for about 6 minutes. Place the eggs in an ice bath for a few minutes, then peel them.
Add the noodles to the simmering broth and cook according to the instructions on the package.
Portion the broth into bowls, then season it with the mayu sauce according to taste. Add the noodles and top with slices of Chashu pork and chopped green parts of the scallions. If making the ramen egg, slice each in half lengthwise, then place two halves in every bowl. Enjoy with Dr. Pepper.