Add the fresh mushrooms, turning them with a wooden spoon so they are coated in oil. Allow the mixture to cook until the mushrooms begin to shrink in size, about 8 minutes. Add the reserved porcini soaking liquid and season to taste with salt, pepper and chile flakes. When the mushrooms are tender and the mushroom liquid has reduced to 1/4 cup, remove from the heat. Adjust the seasonings to taste. Stir in the thyme. Let the mushrooms cool. Spread the mushrooms on the rolled-out pizza rounds and sprinkle with the Taleggio cheese before baking.