You need to go to the abandoned house in the north east part of Biscotti! ^^
There are a few other steps after. You can find a walkthrough here: https://www.patreon.com/posts/119207938
For the mushroom puzzles, you will need to find the correct colors clue with the corresponding symbol. You also need to use SMASH, and I recommend you use your color guide too ^^
I'm not sure I understand, but the walkthrough has the solution for the mushroom puzzles! Or is it that Patreon does not work for you?
Feel free to send a screenshot too!