How to Make It
In a medium heatproof bowl, soak the porcini in the boiling water until softened, about 20 minutes.
Meanwhile, preheat the oven to 350°. Using a sharp paring knife, carefully cut a 2-inch ring around the stems of each dumpling squash; remove and reserve. Scoop out and discard the seeds from inside the squash and those clinging to the tops. Season each squash with salt and pepper and replace the tops.
Set the squash on a baking sheet and bake for 30 minutes, or until just tender. Let cool slightly. Using a teaspoon, carefully scoop the flesh from each squash, leaving a 1/3-inch-thick shell. Replace the lids and reserve the flesh. Leave the oven on.
In a large saucepan, combine the stock with the butternut squash and the parsley and sage sprigs. Bring to a boil, then simmer over low heat until the squash is tender, about 20 minutes. Discard the parsley and sage sprigs. Working in batches, in a food processor, puree the squash with about 1/2 cup of the stock. Return the puree to the sauce-pan, add the reserved sweet dumpling squash flesh and stir to combine. Season with salt and pepper. Keep warm.
Rub the porcini to loosen any grit, discard any tough stems and transfer the mushrooms to a blender. Let the soaking liquid stand for 5 minutes, then slowly add 1/2 cup to the blender and puree. Scrape the puree into a bowl and season with salt and pepper.
In a medium bowl, whip the cream until firm. Fold in the mushroom puree and season with salt and pepper. Reheat the squash in the oven, then transfer to plates and set the lids beside the squash. Stir the chopped parsley into the soup and ladle it into the squash. Spoon a dollop of porcini cream into each soup, garnish with the sage and serve.