• Cook the rice according to the package directions. Remove from the heat and set it aside to cool.
• Soak the dried mushrooms in 1 cup of hot water for 20 to 30 minutes, until soft. Strain the soaking liquid through a coffee filter to remove any grit and reserve the liquid, along with the reconstituted mushrooms, until needed.
• Heat the olive oil and butter in a large (5 quart) Dutch oven or heavy soup pot set over a medium-high heat. Add the crimini and shiitake mushrooms. Toss them in the oil and then cover the pot until the mushroom release their liquid, about 5 minutes. Then remove the cover and cook them, uncovered, stirring occasionally, until they turn golden brown and caramelized, about 10 minutes. Add the onion, and season with some salt and pepper. Cook until the onions are soft and translucent, about 7 minutes. Then add the garlic, thyme and sage and cook until the garlic is fragrant, about 1 minute.
• Stir in a 1/4 cup of sherry, all the stock, the dried mushrooms and the filtered soaking water. Bring the liquid to a boil, then turn the heat down to low and simmer for 30 minutes. Add the other 1/4 cup sherry and simmer for 5 minutes longer. Using an immersion blender, puree the soup until completely smooth (or use a standing blender, working in batches and return the pureed soup to the pot). Stir in the mascarpone and the cooked rice.

To make the Enoki Mushroom and Breadcrumb topping:

• Set an 8-inch skillet over medium-high heat and add one tablespoon of butter or oil. When hot, add the mushrooms and let them brown on one side, about 3 minutes. Turn and crisp the other side. Season to taste with salt and pepper and remove to plate. Add the other tablespoon butter and the grated garlic. Stir until the garlic is fragrant, about 30 seconds, and add the breadcrumbs. Toss the bread in the garlic butter and cook, stirring them often, until the bread browns and crisps. Season with a little more salt and pepper.
• Divide the soup into bowls, and top each with some mushrooms and breadcrumbs.