I've already posted this recipe here (Japanese only) on COOKPAD. Japanese version omitted.
There are a lot of recipes out there for "fake matsutake" gohan, and this particular one is characterized by 1) The mushrooms are not cooked together with rice and 2) the "instant soup" is put after the rice is cooked.
3.5 go (180 ml x 3.5 = 630 ml) rice
2 packets Nagatanien "Matsutake no Aji Osuimono" (instant matsutake soup)
2 tbsp soy sacue
1 tbsp sake
250 g (or 100 g to 200 g) mushroom of your choice)
Note: The mushroom need not necessarily be eryngii!
Put mushroom of your choice (buna shimeji here) in a pot, add soy sauce and sake, plus 150 to 200 ml of water, and bring to a boil.
When it comes to a boil, turn the heat to low, put on the lid, simmer for 3 minutes or so until done.
Immediately separate mushroom from liquid, using a sieve. Cool the liquid.
Wash and drain rice.
Add the liquid to the inner pot (containing the rice).
Wash abura-age lightly. DON'T SQUEEZE because you want the oil in it. Cut in half crosswise first and then into 5-mm widths.
Add abura-age, and pour additional water up to the 3.5 go level. Leave 30 minutes and then start cooking. For an IH rice cooker, you can start cooking immediately.
When the rice is cooked, add mushroom.
Add 2 packets of "instant soup".
Mix well, and it's done!
Cook the mushroom (and chicken and other ingredients if you want) in a separate pot, and after the rice is cooked, mix the mushroom together with the "instant soup". This extra step will ensure delicious takikomi gohan. You won't fail. You may want to add carrot, etc. in the cooker pot right from the beginning together with abura-age.
The other day, I used some eryngii and some dried bunashimeji.