Brown Butter, Rye, and Banana Sourdough Crumb Cake
If you follow me in Instagram, you know that I make a LOT of bread. Specifically, sourdough bread, which requires maintaining a sourdough starter. People lovingly refer to their starters as pets, or even children, but I think of my starter as another friend in the kitchen. Simply put, a sourdough starter is a community of wild yeast that you cultivate using only the power of flour, water, and time. As the natural bacteria present in the grains mature, the starter bubbles, ferments, and grows, becoming “ripe” for a recipe.
Each time you feed the starter, you only need a small bit of the current starter, which is then refreshed with new flour and water. The rest of the starter is now considered “discard.” But that doesn’t mean you should in fact discard it! Many new sourdough bakers are disheartened at the amount of flour they seem to be wasting by throwing out a portion daily while creating their starter. While you can generally maintain less starter once it’s established, sometimes I make a big batch of levain (starter + ingredients specific to a bread recipe) and only need a portion of that for the actual final bread recipe. So there’s generally always a container of discard somewhere in any sourdough baker’s kitchen.
Luckily, my friends Doaa @asoulfulkitchen and Dora @mgracebakeshop decided to host a sourdough collaboration on Instagram and I immediately jumped in. I thought at first I would share a regular loaf, but I decided to get creative and use not one, but two things in my fridge begging to be baked: some discard, and two very ripe, almost-on-the-verge-of-being-compost bananas. It’s the black-peel stage when bananas are truly best for baking, so along came this crumb cake!
The addition of browned butter adds a rich depth to the cake and enhances the nuttiness that the rye flour adds. My starter is 100% whole wheat, so my version of this cake had quite a nice toothsome crumb between that and the full cup of rye flour. A blanket of heavily spiced crumbs on top and a dusting of powdered sugar takes this firmly out of banana bread territory and into crumb cake land, where I will happy be for as long as this cake lasts.
Check out the other bakes from the #sourdoughcollab on Instagram, and enjoy the recipe below!
Brown Butter, Rye, and Banana Sourdough Crumb Cake Recipe
Makes one 8-inch round cake
Ingredients
For the cake:
8 tablespoons (1 stick) unsalted butter
1 cup rye flour
1 cup all purpose flour
3/4 cup brown sugar
1/2 teaspoon baking soda
1/2 teaspoon kosher salt
2 ripe bananas
2/3 cup sourdough discard (unfed)
2 large eggs
1 teaspoon vanilla extract
For the crumb topping:
4 tablespoons unsalted butter, cold and cut into small cubes
2/3 cup all purpose flour
1/3 cup packed brown sugar
1 1/2 teaspoons cinnamon
1/2 teaspoon freshly grated nutmeg
Powdered sugar for dusting, optional
Method
Preheat the oven to 350°F with the rack in the middle. Prepare an 8 inch cake pan by buttering and flouring the inside, tapping out any excess flour.
Make the cake: In a medium skillet over medium heat, melt the butter and allow to simmer until all the water evaporates and the butter is browned. Stir occasionally during this process and use sound as a cue; when the butter becomes quiet, it’s done browning. Remove from heat and set aside to cool slightly.
Combine the rye flour, all purpose flour, brown sugar, baking soda, and salt in a large bowl and set aside.
Mash the bananas in a medium bowl with a fork until smooth. Add the sourdough discard, eggs, and vanilla, and whisk to combine. Stir in the warm, but not hot, browned butter. Pour wet ingredients into dry ingredients and fold until mixture comes together and no dry streaks remain; do not over mix. Allow to sit briefly while you make the topping.
Make the topping: combine the flour, sugar, cinnamon, and nutmeg in a medium bowl. Add the butter and toss to combine, using your fingertips to press butter cubes into dry mixture until you are able to form crumbs with your hands. Some bits will be sandy, others will be large crumbs.
Pour cake batter into prepared pan, and top with crumb topping. Bake for 35-45 minutes, rotating halfway through, or until a toothpick inserted into the center comes out just clean. Take care not to over-bake; slightly under is better than slightly over.
Cool cake on rack until just warm to the touch, then dust with powdered sugar if using. Slice and serve.
Store leftover cake covered on the counter for up to 3 days.
