This was so much fun to make: I just took a rectangle of fabric the width that I wanted the top to ultimately be plus extra for the top and bottom hems. The length was twice the measurement of my girl's chest--which added to a bit less than 44 inches, so I just cut it the width of the fabric and left it at that.
I hemmed the bottom and top of the fabric, and added sparkly purple and white lace trim to the top, and sparkly purple rick rack to the bottom.
Then, I filled a bobbin with elastic thread using the bobbin winder on my Bernina 440 QE--lots of tutes on line suggested winding it by hand, but that bugged the crap out of me, so I used the machine. I tapped the filled bobbin on the table a few times to loosen the elastic up a bit, then loaded it up in my bobbin case like any other bobbin, and popped it in. Then, I threaded the machine with purple thread so it would show nicely on the green, picked up the elastic thread (on the third try, it was a bit finicky about that), set my stitch length to five, and did a test run on a different chunk of material.
When the world did not end, I went on to do ten rows of shirring on my actual fabric, 1/4" apart. At the end of each row, I left the needle in the fabric, turned 90 degrees, took a couple of stitches, turned 90 degrees again and then stitched on, back and forth.
When the shirring was done, I took out the elastic bobbin and loaded up the machine with a bobbin of regular thread, lest I forget.
Then, I took my shirred rectangle over and with my iron on highest heat and full of lots of steamy goodness, I steamed the crap out of the fabric by holding the iron about an inch above the fabric and repeatedly pushed the steam blast button and watched in delight as the fabric shrank up and gathered into delicious wee puckers. It was the best part--like a magic trick.
Then, I stitched it together into a tube and made spaghetti straps of purple fabric using my Fasturn tubes, sewed them on and added a sparkly purple button to the top as an accent and it was done.
The girl was dancing with impatience to try it on as I hand sewed the straps and button on, and she was thrilled to finally wear it today.
It was so easy, I am off to make a dress this evening!