So I will try to propagate some of the mycelium from the oyster mushroom growing kit. I have already done this years ago and it worked fairly well, so I hope these will thrive as well.
The materials for the growing substrate are 500g of rye grains, 25g of gypsum and 500ml of water. Cook this over medium heat, stirring often, until no more liquid is left over in the pan. You want the grains to be evenly covered in gypsum and well soaked but reasonably dry on the surface.
Clean and disinfect some glass jars, poke a hole in the lids and cover it with micropore surgical tape to allow gas exchange. Fill in the mixture, close the lid and let cool. When cooled, take a cutter knife and sterilize the blade in a flame thoroughly, disinfect your hands and, ideally, wear rubber gloves. Cut a piece of about 1.5 cm edge length from the perfoliated mushrooms block, divide it into smaller crumbles and add to the prepared glass jar. Close immediately and store in a dark, moist and cool place.
Growing time for the mycelium varies greatly, so check them every week or so paying close attention to any contaminations (i.e. mold). You’ll recognize them by their greenish or brownish color, whereas the desired mycelium will be white. Throw away any contaminated subtrates. The ones that thrive can later be used for making new mushroom growing blocks. This is not an ultra-clean, satisfaction-guaranteed pro-method, but if you work hygenically and take a little care, the chances of success are fairly good.