Combine chicken breast, bay leaf, peppercorns, and four cups of water in a medium saucepan.
Cover with a lid, place it over medium-high heat, and bring to a boil --- remove any scum floating on top.
Adjust the heat to low and simmer until the chicken is cooked, then remove it from the water and let it cool.
Once the chicken is cool enough to handle, separate the meat from the skin and bones, shredding it with your hands ---- then set aside.
In another medium to large saucepan, heat oil over medium-high heat.
Add garlic and onion and cook until the onion becomes translucent.
Add carrot and celery; mix for a couple of minutes.
Add the chopped hotdog and the shredded chicken, mixing to combine everything.
Use a strainer to pour the liquid from the chicken, then add the bouillon cubes and half a tablespoon of fish sauce. (NOTE: If using a fully-seasoned stock, do not add the fish sauce right away; taste it first!) Cover with a lid, boil, adjust the heat, and simmer for about 20 minutes.
Add the macaroni.
Cover and lower heat --- then continue simmering your sopas until the macaroni is cooked.
Pour the evaporated milk.
Mix, taste, and adjust seasoning by adding ground black pepper or fish sauce.
Remove your pot of chicken sopas from the heat.
Transfer into serving bowls and enjoy!