Preheat your oven to 350°F (175°C). Grease and line a 7-inch round cake pan with parchment paper.

In a large bowl, whisk together the eggs and sugar until the mixture is pale and fluffy. This should take about 3-5 minutes. Sift the flour, baking powder, and salt into another bowl. Gently fold the dry ingredients into the egg mixture, taking care not to deflate the batter. Once combined, pour the batter into the prepared pan and smooth the top. Bake for about 25-30 minutes, or until the cake springs back when lightly pressed. Let it cool completely on a wire rack.

While the cake is cooling, start on the coffee buttercream. In a small saucepan, combine the sugar and water, and heat gently until the sugar dissolves. Bring to a boil and boil for about 5 minutes until it forms a thin syrup. In a separate bowl, whisk the egg yolks until smooth. Slowly pour the hot syrup into the yolks while whisking constantly. Keep whisking until the mixture cools down. In another bowl, cream the softened butter until light and fluffy. Gradually add the cooled egg mixture to the butter, followed by the strong coffee. Continue mixing until the buttercream is smooth and creamy.

Once the cake has cooled, slice it in half horizontally. Spread a generous layer of the crème au beurre moka on the bottom half of the cake. Place the top half back on and press gently to sandwich them together.

Toast the slivered or sliced almonds in a dry pan over medium heat until golden brown. Let them cool. Spread the remaining coffee buttercream over the top and sides of the cake, then press the toasted almonds onto the sides and top. Dust the cake with a little confectioners' sugar for a touch of elegance, if desired.