Bring 1 c water to boil, remove from heat. Carefully add dreid mushrooms and let sit for 30 minutes.
Meanwhile, in large skillet or saute pan, over medium heat, heat oil. When oil is hot add butter then saute green onions until they begin to slightly brown, then add yellow onion and cook until shiny and most liquid has evaporated. Add garlic and herbs, salt & pepper and cook just a minute or so until garlic becomes fragrant. Add white wine, sun-dried tomatoes, button mushrooms and rehydrated mushrooms that have been drained and chopped. Cook until most liquids have evaporated, about 5 minutes. Set mixture aside to cool.
On a floured surface, roll out pie crust and transfer to ungreased dark baking sheet.
In a medium bowl, crumble bleu cheese and add in the mushroom mixture and blend well. Spoon cheese-mushroom filling onto the center of pie crust and spread, leaving a 1-1/2" border. Fold edges of piecrust toward center, pleating to retain a circular shape; the filling will be exposed.
Preheat oven to 400 degree oven. Bake until crust is golden, approximately 25-30 minutes. Remove from ove nand let stand 10 minutes. Slide galette onto a serving plate, garnish with several sprigs of fresh thyme. Cut into 8 wedges and serve.