Let’s break down this elegant cake construction:

1. Prepare Pans and Preheat Oven: Preheat the oven to 160°C fan/180°C/350°F. Lightly grease and line the bottoms of 2 (or preferably 4) 6-inch loose-bottomed cake tins with parchment paper.

2. Make the Cake Batter (Choose Method):

• Food Processor Method: Place room temperature butter, sugar, flour, baking powder, and salt into the food processor bowl. Pulse a few times until combined (resembles crumbs). Add eggs one by one, pulsing 1-3 times after each. Add milk and vanilla seeds/extract; process just until combined. Do not overmix.
• Hand/Stand Mixer Method: Whisk together flour, baking powder, and salt in a medium bowl. In a large bowl or stand mixer, cream room temperature butter and sugar for 3-5 minutes until smooth and light. Beat in eggs one by one, adding a spoonful of the flour mix after each egg to prevent curdling. Beat in milk and vanilla. Slowly mix in the remaining flour mixture until smooth. Beat for no longer than 30 seconds.

3. Divide and Flavor Batter (Optional – for Colored Layers):

• Weigh the total batter. Divide it into three portions: one half (approx. 575g based on recipe example) and two quarters (approx. 287g each).
• Gently fold the 1 ½ Tbsp espresso powder into the largest (half) portion.
• Gently fold the 1 ½ Tbsp cocoa powder into one of the smaller (quarter) portions.
• Leave the remaining smaller (quarter) portion plain vanilla.
• (If not making colored layers, simply divide the plain batter evenly between 2 or 4 prepared pans).

4. Bake Cake Layers:

• Divide the batter(s) evenly among the prepared cake tins (e.g., 1 espresso layer, 1 cocoa layer, 2 vanilla layers if using 4 pans and coloring, or split plain batter between 2 or 4 pans). Smooth the tops.
• Bake for 25-35 minutes (adjust time based on number of pans/layer thickness – thinner layers bake faster) or until a toothpick inserted into the center comes out clean. The recipe doesn’t specify baking time for 4 pans vs 2, estimate around 20-25 for 4 thin layers, 30-35 for 2 thicker layers.
• Let cakes cool in tins for 10 minutes, then invert onto a wire rack to cool completely. If baking 2 layers, carefully split each cooled layer horizontally to create 4 thin layers.

5. Make the Coffee Syrup:

• Combine espresso powder, sugar, and water in a small saucepan. Bring to a simmer, stirring until sugar dissolves. Let cool completely.

6. Make the Mascarpone Frosting:

• In a large bowl (preferably chilled), beat the mascarpone cheese with an electric mixer (paddle attachment or hand mixer) on low speed until just smooth. Be careful not to overbeat mascarpone, as it can curdle easily.
• Add the sifted icing sugar, vanilla seeds/extract, and espresso powder. Beat on low speed until just combined.
• Fold in the finely grated dark chocolate.
• If the frosting is too stiff, mix in 1-2 tablespoons of milk until it reaches a smooth, spreadable consistency. Do not overmix.

7. Assemble the Tiramisu Cake:

• Place one cake layer onto your serving plate or cake board.
• Brush the layer generously with the cooled coffee syrup.
• Spread about 1/4 of the mascarpone frosting evenly over the soaked layer.
• Repeat with the remaining cake layers, brushing each with syrup and topping with frosting. Ensure layers are stacked evenly.
• Apply a thin crumb coat of frosting to the sides of the cake if desired (optional, depends on final look). Chill briefly if doing a full frosting coat.
• Frost the top and sides of the cake smoothly with the remaining frosting, or leave sides exposed for a “naked” look.

8. Finish and Chill:

• Dust the top of the cake generously with cocoa powder using a fine-mesh sieve.
• Refrigerate the cake for at least 2-4 hours (or preferably overnight) to allow the flavors to meld and the cake to set properly before slicing.

Patience during chilling is key for the best flavor and texture!