Walnut trees were cultivated in Persia (now Iran) as early as 7000 BC. In fact, they may have been included in the Hanging Gardens of Babylon. The walnuts we know today, originally called Persian walnuts, were brought to England along the Silk Road. Eventually, English merchant marines began using this hardy, shelf-stable cargo to trade in ports throughout the Mediterranean, thus earning it the moniker English walnut.
Using nuts in culinary applications goes much further back, however. Archaeologists in Israel found evidence that nuts were part of man’s diet 780,000 years ago. There’s even a recipe for a Tiger Nut Cake printed in hieroglyphs in the Tomb of Rekhmire, in Thebes, Egypt, dating back to 1400 BC. (Though technically tiger nuts are tubers and not true nuts, I thought that little factoid was so interesting I wanted to include it.)
Fortunately, Mary Berry’s version of a nut cake, which we are making today, is much lighter and fluffier than that of the ancient Egyptians, thanks to the addition of eggs and baking powder. Her cake features three layers of light, moist sponge with bits of walnut throughout, filled with vanilla buttercream and covered with what she calls boiled icing but what I recall from my childhood as seven-minute frosting.
This fluffy, white, meringue-like frosting is not boiled at all, but whisked over a pan of simmering water until it forms a marshmallowy consistency. (I remember, as a kid, standing by the hot stove for what seemed like hours, whisking the sweetened egg whites until my arms ached.) Once done, it certainly looked pretty swirled all over the cake like a cloud, but I had the same problem most of the bakers in the Great White Tent did in that my frosting came out grainy. I’m not sure how this could have been corrected; if I had continued to beat it longer over the bain-marie I’m afraid it would have been too stiff.
In addition to the cake and frosting, Mary wanted to see caramelized walnuts on top. I have had difficulties making caramel in the past, but I think I’m getting the hang of it. While I’ve had more luck with the dry method, Mary’s recipe uses the wet method, adding 2 tablespoons of water to the sugar before melting it. Having failed at this method in the past, I’ve done a bit of research and learned a few tricks of the trade. So instead of stirring the sugar to try dissolving it in such a small amount of water, I simply poured the water over the sugar and began heating it without stirring. I also put the lid on the pan to help prevent sugar crystals from forming on the sides of the pan, which can cause the entire batch to crystallize. Lifting the lid occasionally, I would also brush the sides of the pan with water if I saw any hint of crystals forming. This time it worked, and I ended up with a nice golden caramel perfect for coating walnuts. I even had enough left over to make some caramel curls by wrapping the cooling caramel around a greased knife-sharpening steel. I used these as added decorations, similar to Ugne’s caramel work on her walnut cake.
The cake itself is not difficult to make. Mary’s instructions to the bakers to “read the recipe twice” and “weigh carefully” is good advice for any baker to follow, no matter how experienced. I did alter it a bit by using three 6-inch pans instead of 8-inch, since I don’t have three 8-inch pans. But because my 6-inch pans are 3 inches deep, I didn’t have to reduce the amount of batter, and they took about the same amount of time to bake as thinner 8-inch layers. If you ever need to scale a recipe to fit different-sized cake pans, I recommend this site.
Most of the Bake-Off bakers did a good job on this technical challenge (despite the grainy frosting), and I think mine could stand up to any of theirs. I got some nice compliments from the neighbors and friends I shared it with, but in my opinion, this type of frosting is just too sweet. I know this is a matter of personal taste — one friend I shared my cake with commented that the icing was a nice change from the “powdered sugar type.” But if I were to make this cake again (and I definitely will!), I would serve it unfrosted, perhaps with a sprinkling of powdered sugar just to make it pretty. It really doesn’t need anything more!
You can find Mary Berry’s recipe here, but I have adapted it for American bakers below.
Mary Berry’s Frosted Walnut Layer Cake
For the cake:
- 1 c. (2 sticks) butter, softened
- 1 c. sugar
- 4 large eggs
- 1¾ c. all-purpose flour, sifted
- 3½ t. baking powder
- ¾ c. walnuts, finely chopped
For the caramelized walnuts:
For the buttercream:
- ½ c. (1 stick) butter, softened
- ½ t. vanilla extract
- 2 T. milk
- 2 ¼ c. powdered sugar
For the boiled icing:
- To make the cake: Preheat the oven to 320°F. Grease three 8-inch round cake pans (or three 6-inch pans if they are at least 3 inches deep) and line the base of each with parchment paper.
- In the bowl of a mixer fitted with the paddle attachment, cream the butter and sugar together until pale and fluffy (about 5 minutes). Beat in the eggs one at a time.
- Mix the flour, baking powder and walnuts together in a separate bowl. Then gently fold the flour mixture into the batter. Divide the mixture equally between the three pans and level the surfaces with a spatula.
- Bake for about 25-30 minutes, or until the cakes are golden-brown and a toothpick inserted in the center comes out clean. Leave to cool in the pans for a few minutes, then turn out, peel off the parchment and finish cooling on a wire rack.
- To make the caramelized walnuts, put the sugar and water in a saucepan and heat over low heat until the sugar begins to melt. (Place a lid on the pan, but check it every couple of minutes. Do not stir, but use a wet pastry brush to brush away any crystals forming on the sides of the pan. Once it begins to boil, watch it closely for it to start turning golden.) Increase the heat and cook the caramel to a dark golden color (CAUTION: Boiling sugar is extremely hot. Handle very carefully). Remove from the heat, add the walnut halves and swirl to coat in the caramel. Transfer the walnut halves to a silicone mat or parchment paper and leave to set.
- To make the buttercream, put the butter, vanilla extract, 1 tablespoon of the milk and half the powdered sugar into a large mixer bowl and beat until smooth. Beat in the remaining sugar. Pour in the rest of the milk, if needed, to make the buttercream spreadable.
- Place the bottom cake layer on a serving platter. Spread half of the buttercream over that layer, and place the second layer on top. Spread the remaining buttercream over the second layer and top with the third layer.
- To make the boiled icing, measure the egg whites, water, sugar and cream of tartar into a heatproof bowl set over a pan of hot water and whisk for 8-10 minutes until thick. Working quickly (the icing sets rapidly), cover the top and sides of the cake with the icing, swirling it to form softened peaks.
- Leave to set in a cool place, but not in the fridge. Decorate with the caramelized walnuts right before serving. (I did keep the leftovers in the refrigerator by cutting individual pieces and storing them in airtight containers. They kept well for a few days.)