First, preheat the oven to 350F/177C and line two, 8-inch cake pans with parchment paper.
In a large mixing bowl, combine all the wet ingredients: sour cream, eggs, cooking oil, honey and vanilla extract. Mix the ingredients together on medium speed for a few minutes until a uniform and smooth mixture forms.
In a separate bowl, combine the dry ingredients: flour, baking soda, baking powder and salt. Sift the dry ingredients into the wet ingredients, then mix for about 1 minute, just until the a smooth batter forms.
Divide the cake batter evenly between the two prepared pans. Bake the cake layers in the preheated oven for 32 to 34 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake layers to cool in the pans for about 5 minutes, then gently transfer them on a wire rack to cool completely.
For Sour Cream Frosting:
Place the softened cream cheese into a large mixing bowl. Beat the cheese for a few minutes until it’s smooth and creamy. Add in the sour cream and vanilla extract and mix again for about a minute.
In a separate mixing bowl (I used my stand mixer), whisk the chilled heavy cream and confectioner’s sugar for 4 to 5minutes, until stiff peaks form.
Add the cream cheese and sour cream mixture into the whipped cream. Whisk on high speed for 30 seconds to 1 minute, scrapping down the sides of the mixing bowl, until a thick and creamy frosting forms.
NOTE: keep the frosting refrigerated when not using!! It tends to melt and soft quickly! If it gets too soft, place it back into the refrigerator and chill it for 15 to 30 minutes. Whisk it again once it’s chilled.
Assembling the Cake:
Finely dice 1 cup of walnuts and dice 1 cup of dried prunes for the filling.
Make sure the cake layers are completely cooled, otherwise they will melt the frosting. Using a serrated knife, first level the top of each cake layer and then split the layers in half. You should have 4 layers total.
To assemble the cake: add about 1 cup of whipped cream frosting onto the cake layer, spreading it evenly to the edges. Next, top the cake layer with a third of the chopped walnuts and chopped prunes, spreading them evenly. Repeat this process for the next 3 layers.
Frost the outside of the cake with a thin crumb coat layer of frosting, then let the cake chill for about 30 minutes. Keep the frosting chilled during this time as well.
Apply the final layer of frosting to the outside, smoothing the frosting with an offset spatula. Garnish the sides of the cake with more diced walnuts, drizzle some melted chocolate over the top and add dollops of whipped cream. I used Ateco tip number 847 for this cake.
Storing & Serving:
Once you have this walnut prune honey cake assembled, it needs to go into the refrigerator. Ideally, leave the cake in the refrigerator overnight to chill and set, or for at least 4 hours. This will allow the cake layers to absorb more moisture from the frosting and allow the flavors to come together. Serve the cake with hot tea or coffee.