The heart of a truly good ramen bowl is all about the broth. Simmer a cut-up chicken for at least 2 hours (or longer if you have time) on the stovetop—or give a slow-cooker or pressure cooker a spin to either allow you to leave the house or speed up the process.
Heat oil in a large stockpot over high heat. Cook onion until charred around edges. Place chicken in pot with the garlic, ginger, and peppercorns. Pour in water. Bring to a boil; reduce heat and allow to simmer, partially covered, for at least 2 hours or up to 4 hours.
After the first hour you can remove the chicken (which will be very tender and falling apart at this point) and pull the meat from the bones. Refrigerate the meat until ready to serve the ramen bowls or freeze the meat to use later.
When the broth is done, strain out the solids and discard. Whisk ¾ cup hot broth with the miso paste until smooth; stir into the large pot of broth.
Ladle broth over noodles in large bowls. Top with some cooked chicken and serve any of the garnishes you’d like alongside, so everyone can customize their bowls.