In a large pot, heat the olive oil over medium heat. Add the onion and garlic and sauté until softened, about 5 minutes.
Add the pearl barley and stir to coat in the oil. Cook for 1-2 minutes until the barley is slightly toasted.
Pour in 1 cup of the chicken broth and stir until absorbed. Continue adding the broth, 1 cup at a time, stirring constantly and waiting for each cup to be absorbed before adding the next.
After 20-25 minutes of cooking, add the diced pumpkin and continue cooking for an additional 10-15 minutes, or until the barley is tender and the pumpkin is soft.
Stir in the cooked chicken and Parmesan cheese. Season with salt and pepper to taste.
Serve hot, garnished with additional Parmesan cheese if desired.