The King Arthur folks posted about these recently, and they looked delicious. They were a little labor-intensive - making the cookies, making the filling, and sandwiching them - but they were so good! As an adult, you don't want to think too hard about the filling, which has marshmallow fluff and shortening (can you hear your arteries hardening?), but I think these would be especially fun for kids. The cookies are soft and cakey, and the filling, once doctored so it didn't taste so predominantly of shortening, tasted perfectly store-bought. I mean that in a good way. The combination was light and sweet and gooey.
Chocolate Whoopie Pies
1/2 cup (1 stick) butter
1 cup (7 ounces) brown sugar
1 teaspoon espresso powder (optional)
1 teaspoon baking powder
1/2 teaspoon baking soda
3/4 teaspoon salt
1 teaspoon vanilla
1 large egg
1/2 cup (1 1/2 ounces) good cocoa
2 1/3 cups (10 ounces) flour
1 cup (8 ounces) milk
1 cup (8 ounces) vegetable shortening
1 cup (4 ounces) powdered sugar (I definitely used more but didn't measure)
1 1/2 cups marshmallow fluff (the recipe noted that this brand is preferable to Kraft or others, which will yield a thinner filling. I will note that I used the whole 7-ounce jar)
1/4 teaspoon salt dissolve in 1 tablspoon water
1 1/2 teaspoons vanilla
Preheat the oven to 350F. Line two baking sheets with parchment paper. I'm sure you could use a silpat instead.
In a large mixing bowl, beat together the butter, sugar, espresso powder (which I promise does not make it taste remotely of coffee, but just enhances the chocolate flavor), baking powder, baking soda, salt, and vanilla until smooth. Add the egg, and beat until smooth.
Add the flour to the batter alternately with the milk, beating until smooth. Scrape down the sides and bottom of the bowl, then beat one last time.
The original recipe says to drop by 1/4 cupfuls, but that would make whoopie pies the size of your head. I used a level tablespoon scoop instead. Using a cookie scoop is great for when you want all the cookies to be a uniform size and shape. I probably got 12 on a sheet, making sure to leave room for them to spread. The larger size bakes for 15-16 minutes; these probably baked for 11-13. Just put a timer on them and check them. They want to be set and firm to the touch. If your finger indents them, they're not done yet.
Take them out of the oven, let them cool for a few minutes, then loosen them from the parchment using a spatula. Leave them on the pan to cool completely, then move them to a wire rack.
Next, make the filling. Beat together the shortening, powdered sugar, and marshmallow fluff until well combined. Dissolve the salt in the water and add it, and the vanilla, to the mixture. Beat until smooth. Then taste. My entire mouth tasted like shortening, so I started to doctor. I first added the rest of the marshmallow fluff (which isn't actually that all much), and then I sprinkled in a little more powdered sugar to get it to the fluffy (not drippy) consistency. I can't remember exactly how much sugar I added, but I'm sure it wasn't more than a cup. Maybe a half-cup? Definitely do this to taste. It should taste kind of processed in that Twinkie filling-type of way, but it should also taste good.
Match up pairs of cookies that are about the same size and shape. Spread a blob of filling on the flat side of one of the cookies. I spread it around reasonably well, but then used the top cookie to squish the filling right out to the edge. I generally skimp a bit on filling, but take a look at the pictures to get an idea of how full they want to be. If you don't use enough filling, you won't see a visible filling layer, which is what you want to see. The good news is that you can always dab a little more filling in there if you need to.
Because these are sticky, I went against my greener nature and wrapped them individually in plastic wrap. It kept them fresh, and I was then able to stack them together in the tupperware with no problem.