From the Super Mario Wiki
The Cooking Disks are a set of six color-coded disks found throughout the various dimensions of Super Paper Mario. Each Cooking Disk that Mario, Luigi, Princess Peach or Bowser insert into a Dining Specializer will upload a new page of recipes that the player can work with. As the Dining Specializer only starts off with one default page, it is recommended to seek out the Cooking Disks to discover new recipes. However, it is not necessary to find the Cooking Disks in order to create any of the recipes on them.
As the Dining Specializer is modelled after the DS Lite, the Cooking Disks themselves are appropriately modelled after DS game cards.
In the PAL version of the game, they are called Cooking Disk 1-7 instead.
 Cooking Disk Locations
 Cooking Disk R (Page 2)
 Cooking Disk W (Page 3)
Located on the third floor of Flopside, this Cooking Disk's location is the mirror equivalent of Cooking Disk R, and can be reached using the same method.
 Cooking Disk Y (Page 4)
Inside Harold and Gertrude's house on the first floor of Flopside. Mario must flip into 3D to reach this Cooking Disk, which is lying on the table.
 Cooking Disk B (Page 5)
 Cooking Disk G (Page 6)
In the first area of Downtown of Crag, head to the east wall where the Save Block is, and flip into 3D as Mario. Use Dottie to shrink Mario, and enter the hole in the wall. Go down the pipe on the other side of the hole, which leads to a flooded room. Enter the other pipe in this room to reach a Whacka, then flip into 3D to reach the chest containing the Cooking Disk.
 Cooking Disk PU (Page 7)
In The Overthere, there is a Warp Pipe behind the easternmost column in Sector 2. Use Mario to flip into 3D, and to reveal a pipe behind the column. Go down the pipe and defeat the Gigabite to make a chest containing the Cooking Disk appear.