Instructions

To make the Hazelnut Cake:

1. Preheat the oven to 175C/350F. Lightly grease a 6" deep cake tin with gluten/dairy free baking spray. 
2. Beat the egg yolks with half of the sugar (25g/ 1/4 cup) and the vanilla extract in a large bowl until combined and pale. 
3. Whisk the bicarb (baking soda) with the hazelnut flour, and add to the egg yolk mixture. Whisk until all combined, about 2 minutes,  the mixture will be very thick and sticky. Set aside.
4. Put the egg whites in the clean bowl of your stand mixer fitted with the whisk attachment (or a large, clean metal bowl if using a hand mixer). Whip on medium high speed until egg whites are frothy and white. Add the salt and remaining sugar. 
5. Whip until soft peaks form - i.e. when you remove the whisk the egg whites will hold a 'peak' that folds over. 
6. Add 1/3 of the egg whites to the hazelnut mixture and use a metal spoon to mix the two together until combined. Add the remaining egg whites and use the spoon to gently mix until completely combined. 
7. Gently pour the batter into your prepared cake tin.
8. Bake for 27-30 minutes, until cake is springy to touch and a skewer inserted comes out clean. 
9. Leave to cool in the tin for 20 minutes, then turn out onto a wire rack to cool completely. Slice the cake in two horizontally to make two cake layers. 

To make the Plum Sauce:

1. While the cake is baking, make the plum sauce. 
2. Put your chopped plums, brown sugar, cinnamon and lemon juice in a small sauce pan and stir to combine.
3. Bring to a boil on a medium heat, and allow to boil for 2 minutes, stirring to keep it from sticking. 
4. Reduce to a simmer and simmer for 5-7 minutes, until the plums are nice and soft and all the sugar has dissolved. 
5. Leave to cool completely. Then put in a blender and pulse 1-2 times. Set aside ready for cake assembly

To make the Cinnamon Frosting:

1.  Put the coconut oil in the bowl of your stand mixer fitted with the paddle attachment (or use an handheld electric mixer) and beat on medium-high speed for 3 minutes, until coconut oil is smooth.
2. Add the cinnamon and 1/3 of the icing sugar, beat on low until fully combined. 
3. Turn the speed up to medium-high and gradually add the remaining icing sugar. You may need to add more or less, depending on your desired consistency.
4. Beat for a further 2 minutes on medium-high speed until fluffy.

To assemble the cake:

1.  Make sure the cake and sauce are completely cooled before assembling.
2. Put one cake layer on your serving stand/plate. Spoon a few tablespoons of frosting on top and spread out evenly. 
3. Spoon half the frosting into your piping bag and snip off the end. Pipe a thick border around the edge of the cake. 
4. Fill the little trench you just made with plum sauce. 
5. Place the other cake layer on top. Spread with more frosting and pipe another border. Fill the middle with plum sauce. Place whole hazelnuts around the edge of the cake
6. Use remaining frosting to spread a thin layer around the sides of the cake. 
7. Serve!