"Preheat oven to 350°F (175°C). Grease and line three cake pans (10-inch, 8-inch, and 6-inch) with parchment paper."
"In a medium bowl, whisk together flour, baking powder, and salt. Set aside."
"In a large bowl, cream butter and sugar until light and fluffy, about 5 minutes."
"Add eggs one at a time, beating well after each addition. Stir in vanilla extract."
"Gradually add flour mixture alternating with milk, beginning and ending with flour mixture. Mix until just combined."
"Divide batter proportionally between the prepared pans, filling each about two-thirds full."
"Bake until a toothpick inserted in center comes out clean (approximately 45 minutes for the 10-inch layer, 40 minutes for the 8-inch layer, and 35 minutes for the 6-inch layer)."
"Cool in pans for 15 minutes, then turn out onto cooling racks to cool completely."
"For the Swiss meringue buttercream, combine egg whites and sugar in a heatproof bowl over a pot of simmering water."
"Whisk constantly until mixture reaches 160°F (71°C) and sugar is completely dissolved."
"Transfer to a stand mixer fitted with the whisk attachment. Beat on high speed until stiff peaks form and mixture has cooled to room temperature, about 10 minutes."
"Switch to paddle attachment and add butter one tablespoon at a time, mixing well after each addition."
"Add vanilla extract and salt. Beat until smooth and creamy, about 5 minutes."
"Level each cake layer and fill with a thin layer of buttercream between layers."
"Apply a thin crumb coat of buttercream to each tier and refrigerate for 30 minutes."
"Apply a final smooth coat of buttercream to each tier and stack using appropriate dowels for support."
"Prepare piping bags with appropriate tips for Lambeth decoration (round tips #3 and #4, star tip #18, petal tip #104)."
"Begin piping basic borders around the base of each tier using round tips."
"Allow borders to crust slightly before adding the next layer of decoration."
"Create overpiped swags, shells, and scrolls following the Lambeth technique, building dimension with multiple layers."
"Add final details like stringwork and extension work to complete the design."
"Allow completed cake to set in a cool, dry place before serving."