And it seems so easy to make also: just cut a (sort of) diamond shape above the bust, then slash and spread the remaining part of the bodice to create pleats. Then sew back together.
I would work with a relaxed version of the bodice for this. The bodice I made with this method comes out very fitted. For this blouse I would just grade it to a bigger size so the blouse has some movement. And it’s easier to take in then release a garment anyway 😛
This is a very similar garment (image from here), with long sleeves, a shirt collar and made in black silk.