Place a large pot over medium-high heat. Saute the onions to soften, 3-5 minutes, then add the garlic. Saute another minute, then the water, salt, and all mushrooms. (If all the water won't fit in you pot, add as much as possible, and add the remaining water after the broth has simmered down a bit.) Cover, turn the heat down a little, and simmer for 1 hour.
Once the mushroom broth has simmered for an hour, strain out all the veggies and keep warm until time to serve.
For the Brown Butter Seared Halibut with Orzo and Mushrooms:
Meanwhile, heat a large skillet of medium-high, and bring a large pot of water to a boil. Thoroughly dry the halibut fillets with paper towels, then salt and pepper both sides.
Cook the DeLallo Organic Orzo according to package instructions. Strain and set aside.
Place the butter in the skillet. Allow it to melt and brown for 2-3 minutes, then place the halibut fillets in the skillet. Sear for 1-3 minutes per side, depending on thickness. DO NOT overcook the halibut. It should be just barely cooked through, to keep its moist flaky texture. Once the halibut it perfectly seared, Place it on a plate and cover with foil to keep warm.
Then add the mushrooms and garlic to the skillet. Saute for 5-10 minutes to soften and brown. Salt and Pepper to taste, then add the sherry. Continue to cook the mushrooms, until the sherry has absorbed.
Place a mound of orzo in 4 shallow bowls. Top the orzo with mushrooms and seared halibut fillets. Pour the mushroom broth in a serving bowl. At the table, allow each guest to pour mushroom broth over their bowl and serve immediately.