A Honey Shroom is a recipe found in the first three Paper Mario games. It is made by mixing a Mushroom or a Volt Shroom with Honey Syrup. It restores 5 HP and 5 FP. In Paper Mario: The Thousand-Year Door, Zess T. will make this for you for free after you give her the Cookbook.
In Super Paper Mario, the Honey Shroom can be cooked up by Dyllis if she is given a Shroom Shake and a Honey Jar. When used, it restores 10 HP and cures Poison.