I like using period names for period things. Cheveçaille is the 12th century French term for a decorated flat yoke on a dress.
While there is not an extant ladies’ court dress which has survived from the 12th century which we can look at and say definitively, “oh, that’s how it was made,” there are extensive descriptions in the literature of the day, and numerous depictions in both sculpture and painting. A recurring feature is a heavily decorated yoke, such as this one from an illustration in a Bible produced in Champagne around the year 1185. In fact, Eunice Goddard, in her work, Women’s Costume in French Texts of the Eleventh and Twelfth Centuries asserted that that the cheveçaille “is one of the distinguishing characteristics of the twelfth century, and one which is not seen in the thirteenth”.
Rather than the very wide type of cheveçaille shown in the illustration above, for my heraldic bliaut (which is already a bit anachronistic) I decided to go with the SCA standard “keyhole” style outline. Looking for inspiration for layout, I started with this design by Jane Stockton in Lochac, and redrew the fleurs as alternating compass stars and ermine spots, both elements used in the heraldry of my household. I wanted it to work up quickly, so I did the embroidery with #5 perle cotton and added black jasper bead details. There is a picture of the finished cheveçaille in my previous post.
I used four stitches/techniques in this work:
The smaller compass stars were done using a “star stitch” technique described here: 
The ermine spots were accomplished using stem stitch as a fill.
Finally, the looping line which unites the elements was done using a braided chain stitch. A tutorial can be found here: 
Stem stitch and Bayeux stitch are demonstrably appropriate to the period. Chain stitches are among the oldest embroidery stitches known, but I don’t know of any use of this particular variant in the 12th century. I just liked the raised look. The star is probably a modern technique and I wouldn’t be surprised if it was invented by the woman whose stitchery blog I linked to above.
The black and white embroidery is simple, but striking and suits the style of the dress very well.