Preheat the oven to 320°F (160°C).

Grease an 8½ × 4½-inch loaf pan with butter and line it with parchment paper, leaving a little overhang on the sides. This will make it easier to remove the cake after baking.

Place the softened butter and granulated sugar in a large mixing bowl.

Beat with an electric mixer for about 3–4 minutes, until the mixture becomes lighter and creamy. Scrape down the sides of the bowl as needed.

Add the egg yolks one at a time, beating well after each addition.

Add the whole egg and continue mixing until everything is smooth and fully combined.

In a separate bowl, whisk together the flour, cocoa powder, and a small pinch of salt.

Gradually add the dry ingredients to the butter and egg mixture. Mix on low speed just until combined. Avoid overmixing the batter, as this can make the cake heavier.

Place the almonds in a blender or food processor and pulse until they are finely ground. Be careful not to process them for too long, or they may begin to turn into almond butter.

Fold the ground almonds into the chocolate batter with a spatula.

Transfer the batter to the prepared loaf pan and smooth the top.

Bake for approximately 35–45 minutes. Begin checking the cake after 35 minutes. A toothpick inserted into the center should come out with a few moist crumbs but no wet batter.

The exact baking time may vary depending on your oven and the size of your loaf pan.

Allow the cake to cool in the pan for about 15 minutes. Use the parchment paper to carefully lift it out and transfer it to a wire rack.

Let it cool completely before slicing. If desired, dust the top with powdered sugar or drizzle it with melted dark chocolate.