In a large pot, melt the butter over medium heat. Add onion, celery, and carrots. Cook until softened, about 5–6 minutes.

Stir in garlic and cook for another 1–2 minutes until fragrant.

Sprinkle flour over the vegetables and stir to coat. Cook for 1 minute.

Slowly pour in chicken broth, stirring constantly to prevent lumps. Add thyme, salt, and pepper. Bring to a gentle boil.

Add cooked chicken and gnocchi. Simmer until gnocchi are tender and float to the top, about 5 minutes.

Stir in heavy cream and spinach. Let simmer until spinach wilts and soup thickens slightly.

Taste and adjust seasoning as needed. Serve hot.