Alright, you folks got me even though I’m still 9 weeks away from the ebook at the library 
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My first attempt at a marble cake!
I wanted something sweet and cakey, took a while to decide between the chocolate chip snickerdoodle cake and the marble cake, but the latter won out because I have a vat of brown butter (I made ghee a few months ago that cooked too long, so now it’s not ghee, sigh).
Changes:
Half recipe (5" tin – took 25 mins)
Modified to half butter and half grapeseed oil (because it will take me a while to get through the cake, and oil cakes keep better).
Tart whole milk greek yogurt instead of sour cream.
A bit of concentrated coffee to thin the chocolate batter.
Tastes lovely out of the oven. The brown butter flavor came through clearly in both the vanilla and the chocolate batters, and has persisted in the finished cake as well.
Will report back how it ages over the next couple of days.
