From the Super Mario Wiki
A Super Shroom is a basic healing item found in Paper Mario, Paper Mario: The Thousand-Year Door, and Super Paper Mario. The Mushroom heals 10 HP for one party member. Unlike other Mushrooms, it has a blue cap. Mario can use it to make Life Shrooms with the basic items. Super Shrooms can be bought in Harry's Shop, Boo's Mansion, Yoshi's Village, Shiver City, Star Haven, Rip Cheato, and Bowser's Castle. White Li'l Oinks also leave them.
In Paper Mario: The Thousand-Year Door, they can be bought at the Souvenir Shop, Twilight Shop, Keelhaul Key Galleria, Sales Stall and Northwinds Mart.
In Super Paper Mario, Super Shrooms can be found within ? Blocks; in this game, they heal 20 HP on contact with the player, as opposed to the usual 10 in the previous two games. Their carry-on equivalent is the Super Shroom Shake.
New Super Mario Bros. and New Super Mario Bros. Wii feature smaller similar-looking mushrooms called Mini Mushrooms.