Place chicken stock in a large pot and bring to a boil over medium-high heat. Place the dried mushrooms in a large bowl and cover with two cups of the boiling stock. Let the mushrooms stand for 5 minutes. Reduce the heat down to low under the chicken stock.
Meanwhile, warm 2 tablespoons of butter in large frying pan over medium-high heat. Add the sliced shiitake mushrooms and sauté until golden brown, stirring occasionally. Season with kosher salt and freshly ground black pepper and set aside.
After 5 minutes, remove the reconstituted mushrooms from the stock and set aside. Line a fine mesh basket strainer with cheesecloth. Pour the liquid (mushroom infused chicken stock) through the strainer back into the pot of simmering chicken stock.
Warm remaining 2 tablespoons of butter and extra virgin olive oil in a large, heavy bottomed saucepan over medium heat. Add the onions and celery to the pan and sauté for 4 minutes. Add the garlic and continue sauté until the vegetables are soft and translucent (but not browned).
Add the pearled barley, stir and continue to sauté for another 2 minutes. Stir in the white wine and cook until most of the liquid has evaporated.
With a ladle, add 1 cup of warm stock and cook, stirring, until the barley has absorbed the liquid. Continue adding the remaining stock, 1 cup at a time. Each time, cook and stir until the barley has absorbed the stock before adding more. Stop adding liquid once the barley is al dente (soft on the outside, a bit firm on the inside). This process takes about 35 – 40 minutes.
Add the soaked mushrooms, sautéed mushrooms and Parmesan cheese. Cook, stirring, for another 2 minutes to rewarm the mushrooms. Season with kosher salt and freshly ground black pepper to taste.
Divide risotto between 4 plates. Top each serving with Parmesan cheese shavings and hand-torn parsley leaves.