Place porcini mushrooms in a bowl and cover with 1 cup of boiling water. Let sit for 15 minutes to rehydrate. When soft, strain the mushrooms, pressing through a mesh strainer. Reserve the liquid and separate any dirt or hard bits from the mushrooms. Finely chop the porcini mushrooms and set aside.

In a 4 or 5-quart Dutch oven or a heavy bottom pot, melt the butter over medium heat. Add the onions and cook for 2 minutes until they start to soften. Add the fresh chopped mushrooms, stir, and cook for 5 minutes. Add the minced porcini mushrooms and garlic then sprinkle with ½ teaspoon salt. Continue cooking for 10 minutes, stirring occasionally. Sprinkle the mushroom mixture with the flour and toss well to coat. Cook for one minute.

Stir the wine into the mushrooms until smooth, scraping up any browned bits from the bottom of the pot, and cook for one minute. Add the reserved porcini mushroom liquid and the chicken or vegetable stock. Add the thyme sprigs, bay leaf, the remaining ½ teaspoon salt, and ground black pepper. Bring to a boil, then reduce to a simmer and cook for 10 minutes, stirring occasionally. Add the cream and cook for 10-15 more minutes until reduced and thickened. Remove the bay leaf and thyme stems. Serve hot.