Biscornu is a French adjective that means "that which has an irregular form, with projections" or "complicated and bizarre."
To a seamstress or an embroiderer, a biscornu is a tiny eight-sided embroidered pillow that can be used as a pincushion, an holiday ornament, key chain/cell phone decoration, a scissor fob, the centerpiece of a wreath, filled with flower petals or herbs to make a sachet... They're great for anything that you can think to do with a tiny cushion. Biscornus can be cross-stitched, embroidered, hardangered (is that even a word?), anything as long as each side is square and the same size. I've even seen patchwork/quilted biscornus. Biscornus are very popular items for stitchers to exchange; there are many biscornu exchanges arranged online through blogs and forums.
Step 1: A note about size
Biscornus can be any size that you desire, only limited by your skill and the materials that you use (the smaller the biscornu, the more difficult it is to turn the corners). I've made biscornus ranging in size from 3/4 of an inch in diameter all the way up to nearly couch cushion size. Most biscornus fit comfortably in the palm of your hand and are made using two pieces of fabric about 4" or 5" wide each. I've chosen to use the slightly-larger-than-average Hallowe'en biscornu that I made for caerbannog for this tutorial because it's easier to see the details.