Preheat your oven to 180°C (350°F). Grease and dust two 8-inch round cake pans with flour.

Dissolve instant coffee granules in a few tablespoons of boiling water and set aside to cool.

Sift together all-purpose flour, baking powder, and a pinch of salt in a mixing bowl.

Cream the softened unsalted butter and granulated sugar until light and fluffy using an electric mixer.

Incorporate the large eggs one at a time, mixing well after each addition.

Blend the cooled coffee mixture and a splash of vanilla extract into the butter mixture.

Gradually mix the dry ingredients into the wet mixture, alternating with the whole milk.

Fold in the chopped walnuts gently and divide the batter evenly into prepared cake pans.

Bake for 25-30 minutes until golden brown and a toothpick comes out clean.

Cool the cakes in pans for 20 minutes, then transfer to a wire rack to cool completely.

Beat softened butter in a clean bowl, gradually adding powdered sugar and brewed coffee until smooth.

Once cooled, frost one layer, stack the second on top, and frost the entire cake. Optionally sprinkle with walnuts.