Place a large pot on the stovetop and turn the heat to medium. Add the mushrooms and cook, turning occasionally, to let them release their liquid. It will take 8-10 minutes. They will be squeaky in the pot as you turn them.

Once any liquid in the pot has evaporated, add the olive oil and yellow onion. Cool for 5-7 minutes until the mushrooms brown. Add the carrots and celery and cook for 5 minutes. Season with salt and pepper.

Add the minced garlic, dry thyme, minced celery leaves, and crushed red pepper to taste. Cook for 1 minute until fragrant.

Add the chicken and toss to coat. Pour in the chicken broth and bring to a boil. Reduce heat and simmer for 30 minutes. Taste and season.

Combine the tahini, lemon juice, and hot sauce in a bowl. Whisk until smooth. If the tahini seizes up and thickens, add water and continue whisking until smooth. It should become a drizzling consistency. You may need anywhere from a splash to ¼ cup water or more.

Return the soup to a boil. Add the orzo and stir regularly to prevent it from sticking. Boil until al dente. Reduce heat to low.

Scoop out 1 cup of the broth from the pot and add it to the tahini to temper it. Stir until smooth.

Pour the tahini mixture back into the pot with the parsley. Stir to incorporate. Simmer for 5 minutes. Taste and season and remove from heat.

Ladle the soup into bowls and garnish with more parsley and a drizzle of olive oil. Enjoy!