Mai has heard a rumor about the massive mass outbreaks and asks you to bring her some Mushroom Cakes in the Alabaster Icelands.

The Request

After you complete Massive Mass Outbreak in the Coastlands, talk to Mai in Jubilife Village outside of Galaxy Hall. There will be a cutscene.

Ten Mushroom Cakes

To craft Mushroom Cakes, you will need Cake-Lure Bases, which you can buy from Choy's General Store in Jubilife Village, and Springy Mushrooms, which can be found in various locations or obtained by catching pokémon.

Go to Secret Hollow

After you have 10 Mushroom Cakes, go to the Icepeak Camp at the Alabaster Icelands. Go north from there to find the Secret Hollow. If there are rocks blocking the entrance, throw a partner pokémon at it to break it open. Go inside, approach the guidance marker, and press A to investigate, then if you are ready, choose to wait for Mai. Hand over the Mushroom Cakes when asked.

Return to the Village

Go to one of the base camps and there will be a cutscene. You will get 30 Aguav Berries. After the cutscene, talk to Professor Laventon to go back to Jubilife Village.

Talk to Mai

Talk to Mai to complete the request.

Reward

Afterward, you get 3 Star Pieces and 30 Iron Chunks.