First the solution of my dumbness:
I had to cut the felted seam out ( the fabric wouldn't bear all the tearing and unstitching) and then I had to cut some length on the other side too. So the pattern is a bit different because of that, but I doesn't seem to have a great effect on it anyway.
The pattern is the Burda 09/2008 Nr. 126 B. All in all I will say it is an easy going pretty quick pattern. I found it refreshing after the whole dress puzzle with a lot of pieces and plaid matching to make something quicker. It is also flattering and easy to fit wit the elastic. It will make a great shirt dress too.
I used flat felled seams (thanks Dalila!) everywhere and it is really a very clean inside:
Certainly they are not perfect - there are a few wonky spots, but I am still happy with them.
What I really messed up is the button placket - in the original Burda pattern it is a complicated thing that is somehow folded backwards. To be honest I wasn't that much into it and thought it is unnecessary work so I didn't even tried to get it...
So what it happened at the end I made the placket just as I always do, but forget to check with the collar width. Consequence - the neckline opening was longer. OK. Next solution - put a small piece of fabric at the extra length and improvise with the collar ending ( Anyway I am always screwing up collars with stand when it comes to attach them to the bodice. Any good online tutorial on that?). OK. Next consequence:
Not sure how they are sewing the cuff in the original modell. I just opted for my standard procedure ( scroll down with the dot com dress and you'll find the tutorial) - iron a bias tape and sew it on. Then I just sewn on the cuffs. Easy.
The elastic is done the same way as with the Coat Elisabeth project. Self fabric stripes are being stitched on and then the elastic is fixed at both ends.
The hem was easy this time - thanks god it is a straight one. I just rolled it and ironed it flat. Next thing I did different as usual is that I fixed it from the inside. Same with the placket. Mostly I hate the fact that on the right side I looks fine but on the inside the seam is to much in or out... Stitching from the inside helps...
The blouse on the outside. I will post next time some images wearing it.