Rhubarb season seems to slip by quickly each spring, and by the time I think of transforming it into a new treat, it’s gone from the market. I’m left with the disappointment of missing something so bright, so refreshing, and so quintessentially springtime. But not this year.
Craving a casual dessert, I decided on a whoopie pie style cookie: soft but sturdy handheld cakes with a creamy filling. After cooking my rhubarb on the stovetop, I incorporated it into both the batter and the filling of these cakey cookies, then paired it with lightly sweetened cream cheese to mirror its tangy flavor. Some vanilla bean and splash of dark rum would offer a complementary, mellow warmth.
Rhubarb Rum Sandwich Cakes (makes about 16 cookie sandwiches, 2.5″ – 3″ diameter each)
FOR THE RHUBARB:
• 1.5 pounds rhubarb, from about 4-6 stalks depending on size
• 2/3 cup sugar
Rinse rhubarb; trim and discard tough ends. Cut each stem in half lengthwise, then cut horizontally in 1/2″ segments. You should have around 4 cups chopped rhubarb, loosely packed. Place it in a medium saucepan and toss with sugar. Place pan over medium heat. Once sizzling, turn heat to medium-low, cover the pan, and cook for 10-15 minutes.
Stop and stir it once after about 5 minutes. Keep an eye on the pan; it’s known to spill over when the rhubarb is quite juicy and nearly finished cooking. When done, rhubarb should be very soft and juicy: easy to mash with a fork. If needed, keep cooking in 5 minute increments and/or increase heat a bit.
Remove pan from heat, remove lid, and let rhubarb sit until it reaches warm room temperature. Measure out a full 1/2 cup of cooked rhubarb and place it in a bowl; mash with a fork until an even pulp is formed, then set aside. Place remaining rhubarb in a non-reactive sieve or strainer over a bowl and set aside. (If not assembling cookies within a couple of hours, cover and refrigerate in a glass container).
FOR THE BATTER:
• 1/2 cup butter, softened
• 3/4 cup sugar
• 2 medium to large eggs
• seeds scraped from 1 large vanilla bean, or 1/2 teaspoon vanilla bean paste or powder
• 1.5 cups flour
• 1/2 teaspoon salt
• 1 teaspoon baking powder
• 2 tablespoons dark/spiced rum**
• ½ cup mashed rhubarb (from above)
Preheat oven to 350 F. Line baking sheets with parchment; set aside. In a large bowl, cream the butter and sugar. Add the eggs one at a time, beating well after each addition. Scrape inside of bowl with spatula while mixing as needed. Add the vanilla bean and beat until evenly dispersed. Over the butter mixture, sift the flour, salt, and baking powder. Begin to mix; batter will be quite thick. Gradually add the mashed rhubarb and the rum, mixing until a smooth batter is formed.
Scoop batter by heaping tablespoons onto lined cookie sheets, keeping 2″ space between dollops. You should have about 32 cookies. Bake 10 minutes, or until edges of cookies are just beginning to look toasty, tops are dry to the touch, and bottoms are golden brown. Remove from oven and let cool completely on baking sheets. They may flatten a bit as they cool. If not filling the same day, store cooled cookies covered up to 24 hours.
FOR THE FILLING & ASSEMBLY:
• 12 ounces cream cheese, softened well
• 1/3 cup powdered sugar, plus extra for serving
• 1/4 teaspoon salt
• 5 teaspoons dark rum
• strained rhubarb from above (set aside its juice to use as you wish)
Beat cream cheese until smooth and soft. Sift the powdered sugar and salt over it. Beat until smooth, stopping to scrape bowl with spatula. Add the rum and beat until incorporated. Store filling covered in the fridge until ready to assemble the cookies (up to 24 hours).
To assemble, turn half of the cooled cookies over and top each one with a rounded tablespoon of cream cheese filling. Add a heaping teaspoon of the strained rhubarb. Top with a remaining cookie, right side up, and press down gently. I like to serve mine in paper cupcake liners and sprinkle them with sifted powdered sugar just before eating.
Rhubarb rum cakes are best when assembled just before eaten, but you can keep them covered and chilled, eating within 12 hours. The powdered sugar and rhubarb will soak into the cookies after much longer than that, but they’ll still taste great up to 48 hours.
Creamy, tangy, and warm at once, these informal little cakes offer vibrancy both to the palate and the eye. The tartness of the rhubarb, the rich creamy filling, and the subtle kick of rum make for an utterly tasty trio. Hearty and decadent, a rhubarb rum sandwich cake is perfect as a standalone dessert or snack. Most of all, it’s a scrumptious way to celebrate the season and catch rhubarb while you can!
**For a stronger rum flavor than this whisper, lightly brush the bottoms of the cakes with more rum before assembling, and/or add another 2 teaspoons of rum to the cream cheese filling. Prefer to not use alcohol? Simply skip it in the filling, and trade it for milk or a not-too-sweet juice in the batter.
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