Purple Sweet Potato Cake with Dark Chocolate Ganache

I’m back at work for a couple of weeks covering a few of my old colleague’s practices for them while they are on vacation.  Working interferes with my baking and other retirement activities but at least I make a bit of extra money and keeps my mind fresh.  I wanted a quick bake of something to bring to work with me, it seems it is expected now, so a quick loaf/cake came to mind.  I was in Chinatown the day before and picked up a couple of pounds of purple sweet potato with this loaf in mind.  I prepared all of the sweet potato by wrapping each in foil and baking them until they were fork tender.  Once cooled I scraped out the flesh and mashed it all, taking out what I needed for this bake while bagging 90 g batches in small ziplock bags which I’ll keep in the freezer for future bakes.

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This was truly a delicious cake, the dark chocolate is rich and smooth, while the cake is moist and tender with lovely spice notes and a mild flavour of the sweet potato.  It was devoured very quickly with lots of compliments.

I did make one big mistake with my first batch of chocolate ganache, unfortunately I kept pot on the burner after adding the chocolate to the simmered cream etc. and the chocolate split.  I tried a few things and couldn’t bring it back together.  I ended up having to toss it all in the bin and run to the store for more dark chocolate.  The second batch went perfectly.

Ingredients

1 lb. sweet potatoes (2–3 medium), peeled, cut into 1" pieces, or 1 cup (250 g) canned sweet potato purée

Unsalted butter or nonstick vegetable oil spray (for pan)

2½ cups (313 g) all-purpose flour

1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt

1 tsp. baking powder

½ tsp. baking soda

2 tsp. ground cinnamon

½ tsp. freshly grated nutmeg

¼ tsp. ground cloves

2 large eggs, room temperature

1½ cups (300 g) granulated sugar (I used 250 g)

2 tsp. finely grated orange zest

1 tsp. vanilla extract

1 cup vegetable oil

GANACHE AND ASSEMBLY

½ cup heavy cream

4 Tbsp. unsalted butter, cut into 1" pieces

3 Tbsp. granulated sugar

2 Tbsp. brewed coffee

½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt

8 oz. (227 g) bittersweet chocolate

½ tsp. vanilla extract

Preparation

CAKE

Step 1

Place a rack in middle of oven and preheat to 400°. If using raw sweet potatoes, wrap in foil and roast on a parchment-lined baking sheet until tender (a knife should slide easily into flesh), 50–60 minutes.

Step 2

Unwrap sweet potatoes and let sit until cool enough to handle. Transfer to a small bowl. Using a potato masher or fork, smash until smooth. Measure out 1¼ cups (250 g) purée; save any extra for another use.

Step 3

Reduce oven temperature to 325°. Butter a 9x5" loaf pan or lightly coat with nonstick spray. Line pan with parchment paper, leaving overhang on long sides. Whisk flour, salt, baking powder, baking soda, cinnamon, nutmeg, and cloves in a medium bowl.

Step 4

Whisk mashed sweet potato (homemade or canned), eggs, granulated sugar, zest, and vanilla extract in a large bowl until smooth. Gradually add oil, whisking constantly until completely incorporated. Using a rubber spatula, fold in dry ingredients in 2 batches, mixing just until combined after each addition. Scrape batter into prepared pan and smooth surface with an offset spatula.

Step 5

Bake cake until golden and a tester inserted into the center comes out clean, 75–90 minutes. Transfer cake to a wire rack and let cool in pan 15 minutes. Using parchment overhang, lift cake out of pan and onto rack. Remove parchment and let cake cool completely.

GANACHE AND ASSEMBLY

Step 6 

Bring cream, butter, sugar, coffee, and salt to a simmer in a small saucepan over medium heat. Remove from heat, add finely chopped chocolate (this will allow it to melt more quickly) and vanilla, and whisk until chocolate is melted and mixture is smooth. If you don’t remove from the heat and heat the chocolate too high it will split and be very hard to fix.  Let cool until thickened slightly, 40–60 minutes.

Step 7

Pour ganache over cake (it should flow over the sides) and, using a small offset spatula, smooth it evenly over surface. Chill cake until ganache is set, 20–30 minutes. Bring cake to room temperature before serving.

 My index of bakes.