Put the water, sherry and mushrooms in a 6 quart dutch oven or crock. Cover and simmer until the mushrooms are hydrated. Let cool. Save any remaining liquid. Slice the mushrooms to desired size. In the same pot, melt the butter and saute the onions and garlic until translucent, add the sliced mushrooms. Whisk in the flour to create a roux. Add the porcini powder and Cedarburg/Ukranian Village seasoning. Slowly whisk in the water, so the roux does not leave lumps. Add the demi glace. Bring the pot to a simmer. Add the cream and bring to a simmer again. Mix in the wild rice. Cover. Keep at a low temperature and stir occasionally to keep the rice from scorching. Once the wild rice is fully cooked, you can uncover the pot and simmer some more for a thicker soup, and adjust the seasoning with black pepper and porcini salt.
Wild rice takes a long time to cook. You may prepare it ahead of time and just add it in the end.