SAEDNEWS: One of the most traditional methods for preserving mushrooms for a long period is drying and grinding them into powder. This method also has a wide variety of approaches. Some people dry mushrooms using a dehydrator machine, others use sunlight, and some use an oven.
According to Saednews, To make mushroom powder at home, you simply need to dry mushrooms completely and then grind them. Different methods can produce slightly different results.
Clean the mushrooms using a damp cloth or a soft brush.
Avoid washing them excessively with water, as moisture makes drying more difficult.
Cut the mushrooms into thin slices (about 3 to 5 mm thick).

In a dehydrator: Dry at around 50–60°C until they become completely dry and brittle.
In an oven: Place them on a tray and dry at the lowest oven temperature (about 50–70°C), leaving the oven door slightly open for ventilation. Dry for 4 to 8 hours. The mushrooms should be dry enough to crumble when pressed.
Place the dried mushrooms in a coffee grinder, food processor, or powerful blender and grind them into a fine powder.
For a smoother powder, sift it through a fine strainer.
Then mix the mushroom powder with:
1 teaspoon salt
1 teaspoon black pepper powder
2 teaspoons cornstarch
Transfer the mixture into a glass container and seal it tightly. This amount yields about 1 cup of mushroom powder.

Store the powder in a sealed glass jar, away from light, heat, and moisture.
Under proper conditions, it stays good for about 6 to 12 months.
Adding to soups and stews
Flavoring sauces
Mixing with spices
Using in meat or vegetarian dishes
Adding to rice, pasta, or omelets for an umami flavor
Only use mushrooms that are completely safe and edible. If you have collected wild mushrooms, consume them only if you are absolutely certain they are safe to eat.