Instructions
Collect a vial of sea water from the crates and barrels that occasionally wash up on shore.
Pick a mushroom. Mushrooms will occasionally appear on land.
Collect stardust when it falls.
Click on the potion icon. Add one stardust, one mushroom and one vial of sea water. Click "Create."
Use the new potion on a female villager.
Select a male villager, then click the female villager on which the potion was used. They will call the stork, and twins will be delivered.