Preheat your oven to 180°C (350°F). Grease and line two 9-inch round cake pans with parchment paper to prevent sticking.

In a large mixing bowl, cream together the softened butter and granulated sugar using an electric mixer on medium speed until the mixture is light and fluffy. This process incorporates air, which helps the cake rise.

Add the eggs one at a time, mixing well after each addition. This ensures that the eggs are fully incorporated, providing moisture and richness to the cake.

In a separate bowl, combine the sifted flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix, as this can lead to a dense cake.

Fold in the chopped walnuts and the dissolved coffee mixture using a spatula. This adds texture and flavor to the cake.

Divide the batter evenly between the prepared cake pans. Smooth the tops with a spatula.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean. This indicates that the cake is fully baked.

Once baked, remove the cakes from the oven and let them cool in the pans for 10 minutes. Then, transfer them to a cooling rack to cool completely. Cooling is essential before frosting to prevent melting.

In a mixing bowl, beat the softened butter until creamy. Gradually add the sifted powdered sugar, mixing on low speed to prevent a sugar cloud.

Add the dissolved coffee and milk, mixing until smooth and fluffy. Adjust the consistency with more milk if necessary.

Once the cakes are completely cool, place one layer on a serving plate. Spread a generous amount of frosting on top.

Place the second layer on top and frost the top and sides of the cake. Use a spatula to create a smooth finish.

Decorate the top with halved walnuts for an appealing presentation.