Green Monet Cake Adventure Part One

“Prue would like you to make an impression of a cake. Quite literally. It’s her version of the impressionist painter Claude Monet’s favorite birthday treat, le gâteau vert.”

The technical challenge on the Great British Bake-Off, known stateside as the Great British Baking Show, was bonkers: three layers of pistachio sponge cake coated in pistachio buttercream covered with homemade pistachio marzipan drizzled with icing colored green using spinach.

I’d never attempted a Bake-Off recipe before, but this green pistachio ridiculousness spoke to me. Online reviews, however, weren’t encouraging. One blogger called the cake “super fiddly,” another strongly suggested against attempting it, and a Bon Appétit writer who spread the process over two days and shelled out $50 for Sicilian pistachios didn’t even follow the recipe. She reported that the cake tasted “fine.”

None of their photos made the cake look remotely appetizing, either, and this is coming from a girl who once ate a green pistachio doughnut that clashed with itself. Yet I was determined. In the calendar for October: a special anniversary, family visiting, and the Denver Art Museum’s big Monet exhibit.

While poring over Prue Leith’s recipe, I told myself that it’s just a cake with buttercream and some interesting stuff on top. Guillaume helped me scope out the best price for bulk raw pistachio kernels. Stella Parks posted a primer on blanching them to achieve tastier results.

Guillaume suggested doing a test-run of just the sponge cake. I’m so glad he did. Even with Prue’s “complete” recipe and all the time in the world, I effed up the genoise. On the show, I’d be one of the contestants who has to start all over again, muttering “pants” while grabbing a clean bowl.

Genoise is notorious. The volume requires perfectly beaten eggs, completely dissolved sugar, and then flour and butter folded just so — oh, and high altitude throws things off.

For the first test-run, I whisked the eggs and sugar on medium-high in the stand mixer for about five minutes, but then made the rookie mistake of dumping the flour, butter, and zest in all at once before folding. Volume lost.

The second test-run, using almond flour in place of the precious pistachio, was only marginally better for height, but the taste was meh.

My third attempt, with the peeled pistachios again plus a pinch of salt, involved being extra patient while the eggs and caster sugar whipped. In theory you should be able to make this cake with an electric hand mixer, but the stand mixer saved my arm.

Volume achieved! It was at least an inch high. And the cake tasted pretty decent, too. Only I waited so long to frost the cake with chocolate buttercream that it lost some height. Even if the rest of this recipe doesn’t work out, I’d feel confident about making the genoise sponge again. Stay tuned for an update on the spinach insanity.

Pistachio Genoise Sponge
25g unsalted butter plus more for greasing pan
50g blanched and peeled raw pistachio kernels, plus extra for decoration
75g all-purpose flour
125g caster sugar
Pinch of salt
4 large eggs at room temperature
Grated zest of 1 lemon (about 1 tsp.)
Chocolate buttercream, for frosting

Prepare the chocolate buttercream, if using, and set aside at room temperature. Grease a 9-inch round cake pan with unsalted butter and line the base with parchment paper.

Preheat the oven to 350°F.

Melt the unsalted butter. Zest the lemon and mix it into the butter. Add a pinch of table salt. Set aside.

Finely grind 50g of raw peeled pistachio kernels in a food processor until it’s pretty fine. Add the 75g of flour and grind that together for a little longer until combined. Remove to a bowl and mix with a fork.

Place the eggs and caster sugar in the bowl of a stand mixer with the whisk attachment. Whisk on low for 1 minute. Switch to medium-high and whisk for around 10 minutes or until the eggs are pale, extremely thick, and tripled in volume. Be patient. The volume can only be lost from here.

Add about a spatula-full of the batter to the bowl with the melted butter and mix it together gently until uniform in texture. This makes the butter easier to incorporate later. Set aside.

Sprinkle about one third of the flour mixture over the top of the big bowl of batter, and fold it in very gently, leaving some streaks. Then do the same with another third of the flour, and then the rest.

Now fold the buttery-batter in gently.

Getting the bowl as close as possible to the prepared cake pan, carefully pour the batter into it, using the spatula as a guide. You don’t want to lose any precious volume.

Bake for 20 minutes or so, until risen and springy to the touch. Check for doneness with a toothpick. Set aside to cool for 5 to 10 minutes, then turn out onto a wire rack to cool completely.

Finely chop about a quarter cup or so of pistachios for decoration. The unpeeled kind seemed fine for this part.

Slice the cooled sponge into two equal layers. Frost the bottom layer with about half the buttercream. Add the second layer and cover the top with the rest of the frosting. Decorate with the chopped pistachios.