Obviously my version is far too closely inspired by Elizabeth Zimmerman's famous design for me to post a full pattern. Although I created this without the original pattern these notes on the modifications I made to the design should work with the pattern.
I wanted to emphasise the lines created by the mitered shaping and to do that I worked the initial decreases as a centered double decrease by slipping 2 together, knitting the next stitch and passing the slipped stitches over it. On the following row I purled this stitch. For the increases I simply worked a m1 on either side of the center stitch and continued to purl this stitch on the wrong side rows.
Other than the different decreases I followed the design of the original until I'd worked 10 ridges while working the increase rows. At that point I slipped all of the stitches of the left front onto a holder (including the centre stitch). I continued working the remaining stitches as per the original, casting off 6 sts at the top of the right side after 4 more ridges to shape the neck. I continued to work the stitches remaining on the needles as established with the mitred increases until the stitches on the needles lined up with the held stitches (I did 14 ridges from the neck shaping). In the end I would have made the shoulders shorter, I ended up re-doing the seams to make the neck wider. Didn't want it irritating a baby neck.
When I came to the left edge I picked up stitches along the vertical edge (one for each ridge) from the right side and then slipped the held stitches from the shoulder side down onto the right needle tip, flipped the work over and knit across them. The rest of the button band border is basically the same as the pattern. I cast off when there were the same number of ridges on the left shoulder as the right - 14. I worked 3 one row buttonholes (from Montse Stanley's directions in The Handknitter's Handbook), using 3 stitches each with 8 stitches in between on the 3rd last row.
I used about 1 and a half skeins of Novita Bambu that my secret pal Heidi sent me and 3.75mm needles. It's about 8" across the chest unstretched. The trim is crab stitch with leftover Rowan Bamboo Soft I'm using for the cardigan I'm working on.
Violetsrose asked: "why is it always knitted in garter stitch? - why can't it be done in stocking stitch? - it would look so much nicer - let us know if theres any intrinsic reason why it can't be done in stocking stitch."
I'm going to answer this question in a slightly circular way, by starting with the answer to the question of why garter stitch is normally used.
Firstly, Elizabeth Zimmerman loved garter stitch, not only because she presumably liked the way it looked and wanted to avoid purling but because it has certain properties that make it ideal for this type of 'architectural' construction.
Obviously garter stitch lies flat, so you don't have to incorporate edgings to prevent curling into your garment.
Generally the row gauge of garter stitch is roughly approximate to double the stitch gauge. This makes things like picking up stitches along a vertical edge simple and it also makes the type of mitered shaping used in this design work simply. If you tried to make a stocking stitch mitered square by either increasing or decreasing on either side of a central stitch on every second row you wouldn't end up with a perfect square that lay flat. There is no reason why you couldn't acheive these shapes in stocking stitch - the point is not that it can't be done, but that it isn't simple. This mitered square afghan pattern suggests that the basic principle of a stocking stitch mitred square would need 3 increases or decreases at the centre rather than 2.
Perhaps the biggest reason for using garter stitch, and the reason I think it would work better for this design than stocking stitch is that garter stitch stretches in all directions. Stocking stitch stretches far more horizontally than in any other direction. Most standard sweater shapes make use of this property to make sweaters that stretch around the body. Clearly the direction of the knitting is not constant in this pattern and so a fabric that stretches in every direction is ideal. A stocking stitch version might not fit so well, or for so long and that's pretty important given how fast babies grow. Personally I like garter stitch, it can work really well with handpainted yarns or interesting textures, but to be honest it is something that has grown on me over time so I can understand why you might not like it. So this design could be worked in stocking stitch, but it would be quite a different sweater and I don't think it would have the same simple neatness of the garter stitch design. I did find a couple of stocking stitch versions, one in progress and one machine knit with cables and ribbed borders that looks like it turned out pretty well.