In a medium saucepan over low heat, combine 1 cup of milk and 8 ounces of chopped white chocolate, stirring until melted and smooth. Once combined, add 2 teaspoons of instant espresso powder, stirring until fully dissolved. Remove from heat and allow the mixture to cool slightly while you prepare the other ingredients.

Preheat your oven to 350°F (175°C). While the oven is heating, prepare three 6-inch round cake pans by greasing them with butter and lining the bottoms with parchment paper.

In a mixing bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of baking powder, and ½ teaspoon of salt. In a separate large bowl, cream together ½ cup of unsalted butter and 1 cup of granulated sugar until light and fluffy. Beat in 3 eggs, followed by 1 teaspoon of vanilla extract. Gradually alternate adding the flour mixture and the cooled chocolate mixture until just combined.

Divide the batter evenly among the prepared cake pans, smoothing the tops with a spatula. Place the pans in the preheated oven and bake for about 35-40 minutes, or until a toothpick inserted into the center comes out mostly clean.

Once baked, remove the cake layers from the oven and let them cool in the pans for about 10 minutes. Carefully run a knife around the edges to loosen the cakes, then invert them onto wire racks to cool completely.

In a heatproof bowl, combine 4 large egg whites and 1 cup of granulated sugar. Whisk together until combined. Place this bowl over a pot of simmering water, whisking constantly until the sugar has dissolved. Remove from heat and using a handheld mixer, whip the mixture until stiff peaks form. Gradually add 1 cup of room temperature butter and 2 teaspoons of espresso powder, continue mixing until creamy and smooth.

In a microwave-safe bowl, combine 8 ounces of chopped white chocolate with ½ cup of heavy cream. Microwave in 30-second intervals, stirring in between, until completely melted and smooth. Allow the ganache to cool to room temperature.

Once the cakes are completely cool, place one layer on a serving plate. Spread a generous layer of whipped white chocolate ganache on top, then add the second layer. Repeat this process with the remaining cake layers.

After stacking, apply a thin crumb coat of ganache around the entire cake to lock in any crumbs, and refrigerate for 30 minutes until set.

After the crumb coat is set, apply a thicker layer of the espresso Swiss meringue buttercream over the entire cake and smooth it out with an offset spatula.

Finish your stunning White Chocolate Mocha Cake with a white chocolate drip around the top edges. Pipe a decorative rope border around the bottom and sprinkle with white nonpareils and dark chocolate crispearls.