This is my perfect whoopee pie: a flat, tender, not-overly-chocolate-y “bun” combined with a less is-more mock buttercream filling. Put the two together and you have sweet-yet-not-too-rich snack that is, in a word, happy-making. Wait, was that two words? Oh well, too late to go back and fix it now. I’ve got to travel tomorrow…I need to pack! Start by preheating your oven to 375 and sifting the dry ingredients together like so:
Combine buttermilk and vanilla.
Put the butter and sugar in the bowl of a mixer fitted with a paddle.
Beat them until they’re good and fluffy, about 3-4 minutes. Then beat in the egg and yolk, scraping the bowl as needed to get a uniform mixture.
Turn the machine down to low and add a third of the flour mixture…
…then half the buttermilk mixture…
…and so on and so on until everything is combined. Scrape the bowl during and after the process.
The batter should be both light and smooth.
Spoon dollops of about three tablespoons in volume onto sheet pans. Six per pan is pretty much perfect, though you can try to sneak a seventh in there…I dunno, it still crowds the sheet I think.
Bake for 10-12 minutes until they’re no longer mushy in the center.
You can either use them as they are, or employ a round cutter to even them out. This is what we did at the bakery, but me, I tend not to like the jagged edge as much.
Selecting one of the lesser-looking rounds, turn it upside-down and pipe on a generous amount of heritage frosting. I prefer this to spreading it with a knife because spreading tends to break and/or crack the tender buns.
Serve right away or store them. One of the glories of a heritage, cooked-flour frosting is that it will keep for days at room temperature without spoiling. Thus these whoopies can be stored, lightly wrapped, on the counter top.
If you want to wrap them individually, you can use plastic wrap, though that tends to make a mess. A thin cellophane is really ideal here, since it won’t stick to the bun. But who am I kidding? These things never last that long…