I am always on the lookout for new (or old), unique techniques for manipulating fabric. I found furrowing in "The Art of Manipulating Fabric" by Collette Wolff.
I tried it out on my daughter's holiday dress in 2008 and was very pleased with the effect. This tutorial is for everyone who requested info on how to achieve this effect.
Step 1: Prepare
Prepare two pieces of fabric - one smaller foundation (called a "stay"), and a larger piece to be gathered to the size of the smaller stay.
In this example I use plain muslin. For simplicity's sake, I have also made both pieces square. In the first photo you can see the baby holding a 4x4 inch square, and in the next she highlights the 6x6 inch square with gathering stitches ready (in red thread).
I have also marked the pieces a grid of dots to illustrate their centers. On the 4x4 inch stay, I marked every inch from the edges; on the larger piece (6x6 inches) I marked a dot for every 1.5 inches.
To Gather - pull the threads to match the size of the larger square to the smaller square on all sides. Pin and stitch the pieces together. The larger piece will form a "puff." This puff is what you will tack with small stitches to form the peaks and valleys that make the furrowed fabric so interesting!