Sweet potato layer cake with spiced pecan buttercream

  • Preparation Time60 mins
  • Cooking Time90 mins
  • Serves10
  • DifficultyHard

For the spiced pecans

250g pecan halves
70g dark brown sugar
2 tbsp ground cinnamon
2 tsp ground nutmeg
70g unsalted butter, melted
2 tbsp dark rum

For the cake layers

900g sweet potatoes
4 large eggs
400g sugar
250ml rapeseed oil
280g cake flour
2 tsp baking powder
1 tsp salt
1 tbsp ground cinnamon
1 tsp ground nutmeg
1 tsp ground ginger
2 tsp pure vanilla extract
3 tbsp rum
125g chopped spiced pecans, recipe follows

For the spiced pecan buttercream

6 large egg yolks
150g sugar
150ml light golden syrup
450g unsalted butter, room temperature
1 tbsp vanilla extract
1/8 tsp salt
125g spiced pecans, recipe follows
Spiced pecans:
1) Preheat the oven to 180C/Gas 4. Place the pecans in a single layer on a baking sheet and toast them for 10 minutes, until fragrant.

2) Combine the brown sugar, cinnamon and nutmeg in a medium bowl, using your fingers to mix everything thoroughly. Stir in the melted butter to make a paste. Add the toasted pecans to the mixture and stir to coat, then spread them evenly on the baking tray and return to the oven for 8 minutes.

3) Remove from the oven, drizzle over the rum, and bake for 8 more minutes, stirring once. Remove from the oven, cool completely but leave the oven on. When cool, chop the pecans into medium-fine pieces, some larger than others, and set aside.

Layer cake:
1) Pierce the sweet potatoes with a fork. Microwave on high until very tender, about 8 minutes per side. Cool, peel, and mash the sweet potatoes with a potato masher or fork.

2) Lower the oven temperature to 160C/Gas 3. Spray 2 (20cm) round cake tins with nonstick baking spray and set aside. In the bowl of an electric mixer fitted with the paddle attachment, beat the eggs and sugar together on medium speed until light and fluffy, 4 minutes.

3) Add the rapeseed oil and beat on medium until combined. Add the mashed sweet potatoes and mix until combined. Sift together the flour, baking powder, salt, cinnamon, nutmeg and ginger and then mix the dry ingredients into the sweet potato mixture. Mix in vanilla and rum. Fold in 125g of the chopped spiced pecans by hand.

4) Evenly distribute the cake batter into the prepared tins, and transfer to the oven. Bake until a toothpick inserted into the centre comes out clean, 40 to 45 minutes. Let the pans cool on a wire rack for 10 minutes, then invert the cakes onto the rack and cool completely.

Pecan buttercream:
1) Make the buttercream whilst the cake is baking. Beat the egg yolks in the clean bowl of an electric mixer fitted with the paddle attachment on medium-high until very thick, about 5 minutes. Combine the sugar with the syrup in a small saucepan, and set over medium-high heat, stirring constantly until the mixture comes to a full boil.

2) Immediately scrape the mixture into a heatproof glass glass measuring cup. With the mixer on high speed, pour a few tbsp of the sugar mixture into the yolks and beat for a few seconds. Repeat until all of the syrup has been added. Beat until the bowl has cooled to room temperature.

3) On medium speed, add the butter, 2 tbsp at a time, beating well after each addition. The frosting will begin to come together after all of the butter has been incorporated (it will look curdled first, but be patient and it will come together beautifully!). Scrape the bowl and beat in the vanilla and salt. Mix in 75g of the chopped spiced pecans.

4) Cut each cooled cake layer in half horizontally, creating 4 layers. Set 1 layer, cut side up, on a cake round or cake plate and spread a thin layer of buttercream on the surface. Stack the next layer on top, and ice. Repeat the icing-and-stacking process until each layer is used.

5) Spread the remaining buttercream on the sides and top of cake. Arrange the remaining spiced pecans decoratively on top of the cake. Chill for 1 hour or serve immediately if you can't wait!

A viewer, who may not be a professional cook, provided this recipe. The Food Network Kitchens chefs have not tested this recipe and therefore we cannot make representation as to the results.

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