Sweet Potato and Rye Coffee Cake
unearthed from the depths of the blog archives
This week, I had a unexpected client project with a tight deadline land in my lap and a sick baby to snuggle and I wasn’t able to get a new recipe completed for you, so we are digging deep into the blog archives and spotlighting one of my very favorite fall recipes. If I’m honest, this Sweet Potato and Rye Coffee Cake is easily in the top 5 of all of the hundreds of recipes I’ve created and it just doesn’t get the love it deserves. So we’re changing that this week. I’m popping in your inbox and shouting it from the rooftops: “Make this cake!”
about the recipe
There are three main components that make this recipe so good: the cake, the crumble, and the glaze.
The cake is thick and pillowy, as any good coffee cake should be. Instead of the classic pumpkin, we’re filling it with caramelized roasted sweet potatoes plus nutty rye flour and a pile of warm spices. We’re using the creaming method here, meaning we cream solid fat (butter) with our sugars for a light, fluffy consistency, but, there’s a little bit of a secret weapon in the form of buttermilk. Buttermilk provides fat and moisture while also tenderizing the cake, making it ultra-moist and a little dense (like an oil-based cake). That means that this final cake is BOTH light and dense, fluffy and moist. It’s everything to everyone and I love it.
On top of the cake is a classic crumble topping. This one has your traditional cast of oats, butter, and flour, but is also spiked with that rye flour, brown sugar, and lots of freshly grated ginger. It’s sweet and tangy and complements the sweet potato cake perfectly.
Finally, on top of our finished coffee cake, there’s a browned butter glaze that is so good I could quite literally eat it with a spoon.
and a few helpful notes
on the sweet potatoes: I love using sweet potatoes in this recipe because pumpkin can be a little overdone in the fall baking season, but this recipe is extra adaptable and you could really use any roasted gourd you’d like—or even sub in canned pumpkin or squash puree. If you decide to stick to the recipe and use sweet potatoes, they need to be soft and mashable. I like to poke holes in a whole sweet potato and then roast it in a 400° F oven for 30-40 minutes until soft. I let it cool completely (sometimes even just pop it in the fridge overnight) and then peel it cold and let it come to room temperature.
on ingredient temperatures: In this cake, it’s helpful to make sure that everything is room temperature before mixing. This cake is a little sensitive and has a tendency to curdle up a bit if any ingredient is even a little bit too cold. If your batter does curdle, especially after adding the eggs and the sweet potato, all is not lost, just add a little of your dry ingredients. The starches will help bind everything back together.
on the glaze: You’re going to see in the recipe that I call for “about 1/4 cup of heavy cream”. It’s a very vague measurement and for that I am sorry, but I’ve made this recipe many times and I think I use a slightly different amount every time. I would recommend starting with 3-4 tbsp of heavy cream and adding more if needed to loosen the glaze. If your glaze begins to separate and become oily, just add a little more heavy cream and keep whisking. The fat in the cream will help it emulsify and come back together. If you get a little heavy handed and your glaze is too runny, add a little more powdered sugar- it’s very forgiving!
sweet potato and rye coffee cake
makes one 9x13” cake
Ingredients:
for the ginger crumble:
1/2 cup (65 g) rye flour
3/4 cup (75 g) rolled oats
1/2 cup (100 g) brown sugar
1/2 tsp ground cinnamon
1/2” piece of fresh ginger, grated (or 1/2 tsp ground ginger)
1/2 tsp kosher salt
1/2 cup (113 g) unsalted butter, softened
for the cake:
1 1/2 cup (190 g) all purpose flour
3/4 cup (100 g) rye flour
1/2 tsp baking powder
1/2 tsp baking soda
3/4 tsp kosher salt
1/2 tsp ground cinnamon
1/4 tsp ground cardamom
1/4 tsp ground nutmeg
1/4 tsp ground ginger
3/4 cup (170 g) unsalted butter, softened
1 cup (220 g) granulated sugar
1/2 cup (100 g) brown sugar
3 eggs, at room temperature
2 tsp vanilla extract
3/4 cup (150 g) sweet potato, cooked and mashed*
1 cup (242 g) buttermilk, at room temperature
for the glaze:
1/2 cup (113 g) unsalted butter
1 1/2-2 cups powdered sugar
pinch of salt
about 1/4 cup heavy whipping cream
Procedure:
to make the crumble:
In a medium bowl, whisk together flour, oats, brown sugar, cinnamon, ginger, and salt.
Add butter and work together using your fingers until butter is completely mixed in and no dry spots remain. Place the crumble in the refrigerator to chill while you make the rest of the cake.
to make the cake:
Preheat oven to 350°F and line a 9x13” baking dish with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, combine butter, granulated sugar, and brown sugar. Beat on medium speed until light and fluffy, about 2 minutes, making sure to scrape down the sides and ensure all butter chunks are mixed in.
Meanwhile, in a medium bowl, whisk together flour, rye flour, baking powder, baking soda, salt, cinnamon, cardamom, nutmeg, and ginger. Set aside.
With the mixer on low speed, add eggs one at a time, mixing each completely before adding the next. Scrape down the sides of the bowl and then add mashed sweet potato and vanilla extract. Mix on low-medium speed for 1-2 minutes more, until everything is combined and homogenous.
With the mixer on low-speed, add 1/3 of the dry ingredients, followed by half of the buttermilk. When the buttermilk has mixed in, add another 1/3 of the dry ingredients, followed by the remaining half of buttermilk, then the remaining 1/3 of the dry ingredients. Scrape down the sides of the bowl and then mix one more minute. Remove bowl from mixer and use a rubber spatula to gently fold the batter a few more times, ensuring that the batter is smooth and homogenous and everything is well combined.
Pour batter into prepared baking dish and use an offset spatula to smooth into an even layer. Remove crumble from refrigerator and sprinkle evenly over the top of the cake.
Bake for 45-50 minutes, rotating the pan halfway through the baking time, until a cake tester or toothpick comes out clean when inserted into the center of the cake. Let cool completely in the pan while you make the glaze.
to make the glaze:
Place butter in a small saucepan set over medium heat and cook for 6-7 minutes, swirling occasionally, until butter is foamy and fragrant and small amber flecks appear on the bottom of the pan.
Quickly remove the butter from the heat and pour into a heatproof bowl. Immediately whisk in powdered sugar, salt, and heavy cream, adding more heavy cream if needed to achieve your desired consistency. Drizzle glaze over coffee cake and let set before slicing.