Best Walnut Cake with Vanilla Icing

Ingredients

For the recipe

• 125 g raw walnut kernels, weighed before toasting, for grinding into the cake batter
• 25 g raw walnut kernels, weighed before toasting, for the topping
• 175 g plain all-purpose flour, divided into 30 g for grinding with the walnuts and 145 g for the remaining dry mixture
• 1 1/2 teaspoons baking powder (6 g)
• 1/4 teaspoon fine salt
• 150 g unsalted butter, softened but not melted, for the cake
• 5 g unsalted butter, for greasing the pan
• 175 g fine white granulated sugar or caster sugar
• 3 large eggs, approximately 150 g without shells, at room temperature
• 100 ml whole milk, at room temperature
• 1 teaspoon vanilla extract (5 ml), for the cake
• 125 g icing sugar or powdered sugar, sifted, for the icing
• 1/2 teaspoon vanilla extract (2.5 ml), for the icing
• 15 ml water, for the icing, added gradually

Instructions

1. Heat the oven to 160°C / 320°F conventional, or 140°C / 285°F fan. Put the 125 g cake walnuts and the 25 g topping walnuts in separate, clearly defined areas of a small rimmed baking tray, spreading both portions into single layers.
2. Toast the walnuts for approximately 8-12 minutes, using 10 minutes as a planning estimate, and stir each portion once halfway through. They should smell fragrant and look slightly deeper in color, without dark or scorched edges. Transfer the two portions to separate plates and let them cool completely, approximately 20 minutes.
3. Increase the oven to 175°C / 350°F conventional, or 160°C / 320°F fan. Grease a 20 cm / 8-inch round metal cake pan, at least 6 cm / 2 1/2 inches deep, with the measured 5 g butter. Line the base with a circle of baking parchment.
4. Put the cooled cake walnuts into a food processor with the measured 30 g flour. Pulse briefly, scraping the bowl as needed, until the nuts form a fine, slightly grainy meal. Stop before the mixture becomes oily or pasty. Chop the cooled topping walnuts and set them aside.
5. Whisk the remaining 145 g flour with the baking powder and salt, then stir in the ground walnut and flour mixture until evenly combined.
6. In a large bowl, beat the 150 g softened butter and sugar with an electric mixer for approximately 3 minutes until lighter and fluffy, scraping the bowl once or twice. The butter should be pliable rather than melted or greasy.
7. Beat in the eggs one at a time, mixing for approximately 20-30 seconds after each addition. Scrape the bowl between eggs and mix in the 5 ml cake vanilla. If the mixture looks slightly separated, continue with the dry ingredients rather than beating it for a long time.
8. Add half the walnut and flour mixture and fold gently. Fold in the milk, followed by the remaining dry mixture. Scrape the bottom of the bowl and stop as soon as no dry flour remains. The batter should be thick but spreadable.
9. Scrape all the batter into the prepared pan, spread it evenly and smooth the top. Tap the pan gently once on the counter to release large air pockets.
10. Bake on the centre rack for approximately 45-55 minutes, using 50 minutes as a planning estimate. Begin checking at 45 minutes. The cake should be golden, the centre should spring back lightly and a skewer inserted into the centre should come out clean or with a few moist crumbs, not wet batter. If the surface browns before the centre is ready, cover loosely with foil for the remaining baking time.
11. Leave the cake in its pan on a rack for 15 minutes. Loosen the edge carefully, turn it out, remove the parchment and place the cake right-side up on the rack. Let it cool completely, allowing approximately 90 minutes in total including the time in the pan.
12. Put the sifted icing sugar into a small bowl with the remaining 2.5 ml vanilla. Stir in the measured water a little at a time until the icing falls from the spoon in a thick ribbon. Stop adding water if the icing is already spreadable; a thinner coating will run off the cake.
13. Transfer the completely cooled cake to a serving plate. Spread all the icing over the top, gently guiding a little toward the edge. Scatter all the reserved chopped walnuts over the icing while it is still soft.
14. Leave the icing to set for approximately 20 minutes, then cut the cake into 12 equal wedges. Use a clean knife and wipe it between cuts for neat slices.
15. Once the icing has set, cover the cake to protect the cut surface and keep the crumb from drying out. Serve at room temperature for the softest butter-cake texture.