Tea bag folding has been around a long time and ranges from simple to very intricate. I did a simple fold on eight squares and then interlaced them to form a "star" shape.
Here are a some tutorials to get you started":
What The Buz is About
Stamping with Lisa Tedder
Origami Resource Center
Ruby's Tantalizing Designs
The cow itself is a twisted pyramid which is done in the same way you do a regular pyramid except that the segments are differently shaped.
On the inside I used some more sections of the sheet and found a different cow picture to finish it off.