Found the dress!
Here I am in the store sample. This is actually three separate pieces, so a bit mix-and-match but you could probably never tell! The top is Oscar de la Renta, skirt is Monique Lhullier, and sash is also Oscar (but I'm having mine made from leftover trimmings from the skirt, so the fabric matches exactly).
The back
The skirt is called the "Meringue" and really does remind me of the dessert! I fell in love with it as soon as I put it on. So comfy :) Apparently it's the same one Vanessa Minillo wore to her recent wedding, haha.