1) Char the aromatics
Heat a large pot over medium-high heat. Add the oil. Place the onion halves and ginger halves cut-side down in the pot. Let them sit until well browned with a few charred spots, 5 to 7 minutes. Flip and give them another 2 minutes. You are building that smoky, sweet backbone.
2) Toast the spices
While the onion and ginger char, toast the star anise, cinnamon, cloves, and coriander seeds in a dry skillet over medium heat until fragrant, 1 to 2 minutes. Stay close. They go from perfect to bitter fast.
3) Simmer the broth
Add the toasted spices to the pot with the onion and ginger. Pour in the chicken broth and water. Bring to a gentle simmer. Add fish sauce, brown sugar, and salt.
Slide in the chicken thighs. Keep the broth at a low simmer, uncovered, until the chicken is cooked through, 15 to 18 minutes (breasts may cook a bit faster). You are looking for 165°F/74°C in the thickest part, or no longer pink in the center. Skim off any foam that rises in the first few minutes for a cleaner broth.
Remove chicken to a plate. Let the broth continue to gently simmer 10 more minutes to mingle.
4) Strain and season
Set a fine mesh strainer over a clean pot or large bowl and strain the broth. Discard the solids.
Taste the broth. This is where it becomes pho. Adjust with a bit more fish sauce for savory depth, a pinch more salt for structure, or a little sugar to round the edges. Keep it hot on low.
5) Cook the noodles
Bring a medium pot of water to a boil. Cook rice noodles according to package directions until tender but still a little springy. Drain and rinse briefly under cool water to stop the cooking.
Divide noodles among 4 bowls.
6) Build the bowls
Thinly slice the chicken. Add a few slices to each bowl. Ladle the hot broth over top.
Finish with scallions, bean sprouts, cilantro, basil, and a squeeze of lime. Add chiles, hoisin, and sriracha at the table if you want that sweet heat swirl.
7) Serve
Pho is at its best in the first 10 minutes. Put everything on the table, let everyone customize, and do not be shy about tasting the broth again with a final lime squeeze.
