Dried mushrooms must be rehydrated and thoroughly cooked.
Place mushrooms in a bowl and add suggested volume of tepid water, not hot. Some mushrooms will float, so make sure they all get wet. Let them stand for 5-20 minutes. Thick pieces, stems, and some varieties take longer so give them a pinch with your fingers to check readiness. If they are plump, they are ready. Take the mushrooms out of the water, squeezing access liquid, and chop, slice, or blend as needed. Always save this water as it has loads of flavour and is used later in the recipe. When pouring the soaking water into your pot or pan, leave the last few tablespoons in the bowl as any bits of nature will have settled to the bottom.
Dried wild seaweed can be eaten raw and sprinkled into any dish, but is best rehydrated for 5 minutes in cool tap water. You can crumble it and then soak it, or soak it and then chop it fine. The seaweed will expand a lot, quite quickly. Soaking activates the mucilage which is a rich, soothing glycoprotein also found in flax, aloe vera. You do not need to save this water.