There are occasions when I wish I had the time and money to work more intensely on recipe development. This cake has the potential to be something really special but it needs a lot more work, and yet I know my family won't want to eat slightly varied versions of the same cake for the next few weeks (particularly as it isn't chocolate!). It might be several weeks before I feel I can have a second attempt at this recipe.
The intention was to layer vanilla madeira cake batter (is this the same as what is known as pound cake in the US?) with more of the cake batter flavoured with pistachios and lemon curd. I expected the lemon curd to change the consistency of the cake batter and thought that it might form moist, gooey layers within the cake. I hoped the pistachios would colour this layer green, so that it would stand out as a differentiated layer, and I could see how it spread while the cake was baking. This didn't happen, because I didn't grind the pistachios to meal, just chopped them in a mini-processor to give a mix of coarse and fine lumps - there wasn't enough fine meal to colour the lemon layer, but I was worried that nut meal would make the lemon ripple too dry.
The finished cake was delicate in flavour, but rich and moist in texture, with a tender, close crumb. It was too difficult, for the most part, to differentiate between the vanilla and lemon/pistachio areas. I have a suspicion that, apart from a patch at the bottom of the cake, the lemony layers blended with the vanilla as the cake cooked, but I won't know this for sure unless I colour the lemon layer. The rich, even moistness of the cake is what suggests to me that the layers merged during cooking.
There wasn't enough lemon flavour from the lemon curd alone, so this is another area which needs work. The next step would probably be colouring the lemon/pistachio layer with added food colour, to see if it stays separate, and adding some lemon zest to boost the flavour.
225g unsalted butter, softened
225g caster sugar
275g SR flour
1 teaspoon vanilla extract
milk, as necessary
75g pistachio nuts, divided, see note
100g lemon curd
note - chop the pistachios to give a mixture of fine and coarse pieces, then remove about 25g of the larger pieces to top the cake.
Pre-heat the oven to 170C, and prepare your cake tin. I used a 30cm long, narrow loaf tin with the same capacity as a 2lb loaf tin. This is roughly the same volume as a round 8"(20cm) diameter tin. I used a sling of baking parchment covering the base and the long sides of the tin.
Cream the butter and sugar until light and fluffy, then beat in the eggs one at a time, with a tespoon of the flour, to prevent curdling. Fold in the rest of the flour with the vanilla extract and enough milk to give a dropping consistency.
Weigh 250g of the batter into a small bowl and stir the 50g portion of nuts and the lemon curd into this smaller amount of batter.
Layer the two batters into the prepared tin in this order, spreading each one to make an even layer before adding the next: 1/3 of the vanilla; 1/2 the lemon; 1/3 vanilla, rest of the lemon, rest of the vanilla.
Sprinkle the remaing nuts evenly over the top and press them lightly into the batter. Bake the cake for about 70 minutes until a tester is clean. You may need to cover the cake for the last 20minutes or so, if it is browning too fast. Cool in the tin for 15 minutes, then move to a wire rack.