Cover the shiitake stems with 5 cups of water in a medium sauce pan and bring to a boil.
Reduce temperature to a simmer for 20 minutes. Strain through a sieve lined with a cheesecloth. Discard stems and reserve mushroom water for future use.
In Dutch Oven, heat olive oil on medium heat. Add garlic and toss.
Add shallot and reduce heat to low. Cook, stirring frequently until shallots are soft. Approximately 5 minutes.
Add the portobello mushrooms, 1 tsp of salt and pepper, toss and cook for 3 minutes, stirring occasionally.
Add the shiitake mushrooms, 1 tsp of salt and pepper, toss and cover for 5 minutes.
Add white mushrooms, 1 tsp of salt and pepper, toss and cover for 5 minutes.
Add chicken broth and simmer for 15 minutes.
Add sherry vinegar, and adjust salt and pepper to taste.
Add thyme, parsley, and cook over medium heat for 10 minutes until mushrooms are tender and most of the liquid has been absorbed.