Let’s assemble this sophisticated Tiramisu Cake layer by layer:

1. Prepare Oven and Pans:

Preheat oven to 160°C fan/180°C conventional/350°F. Lightly grease and line the bottoms of two 6-inch loose-bottomed cake tins with parchment paper. Grease the parchment and flour/cocoa-dust the pans. (You’ll bake in two batches if you only have two pans).

2. Make the Cake Batter (Choose Mixer or Food Processor Method):

• Mixer Method: Whisk flour, baking powder, and salt in a medium bowl. In a stand mixer (paddle attachment), cream room temp butter and sugar for 3-5 mins until light and fluffy. Beat in room temp eggs one by one, adding a spoonful of the flour mix after each egg to prevent curdling. Beat in milk and vanilla seeds/extract. Slowly mix in remaining flour mixture until just smooth (max 30 seconds).
• Food Processor Method: Place room temp butter, sugar, flour, baking powder, and salt in the food processor bowl. Pulse until combined (like breadcrumbs). Add room temp eggs one by one, pulsing 1-3 times after each. Add milk and vanilla seeds/extract and process just until combined. Do not overmix.

3. Divide and Flavor Batter:

Weigh the total batter. Divide it into three portions: Half (approx. 575g based on recipe estimate) and two Quarters (approx. 287g each). Into the largest (Half) portion, carefully fold in the 1 ½ tbsp espresso powder until combined. Into one of the smaller (Quarter) portions, carefully fold in the 1 ½ tbsp cocoa powder until combined. Leave the remaining smaller (Quarter) portion plain vanilla.

4. Bake the Cake Layers:

Split the coffee-flavored batter between the two prepared 6-inch tins. Level the tops. Bake for approximately 25 minutes, or until a skewer inserted comes out clean. Cool in tins for 5 minutes, then remove and transfer to a cooling rack. Clean, re-grease, and re-line the tins. Pour the vanilla batter into one tin and the chocolate batter into the other. Bake as above. Cool completely.

5. Make the Coffee Syrup:

While cakes bake/cool, place espresso powder, sugar, and water into a saucepan. Bring to a boil, stirring until sugar dissolves. Remove from heat and let cool completely.

6. Make the Mascarpone Frosting Base:

Place the cold-but-pliable mascarpone into a large bowl. Add the sifted icing sugar, 1 tablespoon of milk, and the vanilla seeds/extract. Using a spatula, gently stir everything together until the mixture is smooth. Do NOT use an electric mixer initially, as mascarpone can split easily. Add the second tablespoon of milk only if absolutely necessary for smoothness.

7. Divide and Flavor Frosting:

Separate off two portions of frosting, each weighing 125g, into two smaller bowls. Leave the rest (the largest portion) as the vanilla base. Gently stir the cooled melted dark chocolate into one of the smaller 125g portions until combined. Gently stir the 1 teaspoon espresso powder into the other smaller 125g portion until combined.

8. Assemble the Cake:

Level the tops of the completely cooled cakes if needed. Place the chocolate cake layer onto your cake board/stand (use a turntable if possible). Brush the layer generously with the cooled coffee syrup. Evenly spread ⅓ cup of the vanilla mascarpone frosting on top. Place a coffee cake layer on top. Brush with syrup. Spread with ⅓ cup vanilla frosting. Place the second coffee cake layer on top. Brush with syrup. Spread with ⅓ cup vanilla frosting. Place the final vanilla cake layer on top. Brush with syrup.

9. Crumb Coat and Chill:

Using about ⅓ cup of the remaining vanilla frosting, apply a very thin layer all over the outside of the cake (crumb coat). Place the cake in the fridge to set for at least 15 minutes.

10. Apply Ombre Frosting (Optional):

Starting with the chocolate mascarpone frosting, pipe or roughly apply it around the bottom quarter of the chilled cake. Apply the coffee mascarpone frosting to the next quarter up the cake, slightly overlapping the chocolate layer. Cover the rest of the cake (remaining half and top) roughly with the vanilla mascarpone frosting.

11. Smooth the Frosting:

Using a bench scraper held vertically against the side and a rotating turntable (or careful hand movements), smooth the frosting around the sides of the cake. The overlapping colors will blend slightly, creating the ombre effect. Use an offset spatula to smooth the top. Apply any leftover frosting to touch up as needed. (Alternatively, just frost smoothly with vanilla or create a rustic texture).

12. Final Chill and Dusting:

Chill the finished cake briefly if needed. Just before serving, dust the top generously with cocoa powder using a fine-mesh sieve. Slice and serve!