Heat oil in a large stock pot or Dutch oven over medium heat. Once hot, add the onion, carrots, and celery. Cook for 10 minutes, stirring occasionally, until softened. Add the garlic and thyme; cook 1 more minute, until aromatic.
Add broth and increase heat to bring mixture to a boil. Once boiling, add the chickpeas and orzo. Simmer soup over medium-high heat, uncovered, for 10 minutes, or until the orzo is al dente. Reduce heat to low.
Remove about 1 1/2 cups of soup and add to a blender with the tahini. Puree until smooth then pour back into the pot. (Or use an immersion blender to partially puree the soup.)
Add kale and continue to cook over low heat for 5 minutes, or until greens are wilted.
Stir in juice and zest from 1 lemon (taste and add more from second lemon if needed), fresh dill and taste/adjust seasonings as needed. Ladle soup into bowls and garnish with extra fresh dill, cracked black pepper, and a drizzle of olive oil, if desired.