This is made from one of the original patterns released by Pleasant Company, they have since been discontinued, but you can download a printable version at AG Play Things, they print out well, I chose to just print the pattern pages, and read the directions on my ipad.
I really wanted to do a full tutorial on these, but I had some difficultly with the collar facing, they look ok but aren’t perfect.
I made them out of my own old pj bottoms, plain white cotton, some baby white ricrac and Wal-Mart tiny buttons, they are pretty cute! For the sash I used a coordinating piece of grosgrain ribbon.
One tip is to make yourself a template for that tiny little pocket, you fingers will thank you.

I also used blue tape as a seam guide. For the ricrac I recommend using a washable glue stick instead of pins.

Some finished photos to help you if you try and make these.
(The back seam is from the upcycling the fabric).