The Peter Pan collar from our childhoods has boomeranged as one of the biggest trends of this year.. For me this was definitely more a nostalgia sew than following a trend, and I was in the mood for teaching myself something new - I've only sewn regular shirt collars before. For this dress I used a secondhand screen printed silk I found back home in Finland - it's got such a luxurious feel. Of course working with a less flimsy material like linen or cotton would be an easier choice if it's your first time with a collar, but I've found lately I prefer projects that take a while to finish and have complexity/challenges. I'm over the easy sew.
I'm gonna show here also how I constructed the top with the keyhole back, if you're here for the collar only, just scroll down. Same method could be used to add a collar to an existing top with a keyhole back.