Heat the oil in a large pot over medium heat. Add fennel, leek, and onion. Cook about 5 minutes, until softened and fragrant.
Add grated garlic, celery, carrots, and turmeric. Stir and cook another 5 minutes, letting the turmeric bloom and the garlic melt into the base.
Season with salt and pepper, then pour in the chicken stock. Bring to a gentle simmer, cover partially, and cook for 20 minutes, until vegetables are tender and the broth turns golden.
Add shredded chicken and pastina. Simmer 8–10 minutes, stirring occasionally, until pasta is al dente and broth slightly thickens.
Taste and adjust seasoning with more salt or pepper if needed.
Ladle into bowls, top with herbs and fennel fronds, and drizzle olive oil for a glossy finish.