This cake rises purely from whipped eggs—if it isn’t thick enough, whip 10 minutes longer. Room-temp eggs matter here. They whip higher and faster. | You cannot overwhip buttercream. More mixing = creamier texture + more volume. | Keep strokes short (about ½ inch) and work in one direction. If your kitchen is warm, chill the frosting 5–10 minutes before piping. | Génoise: airtight at room temp up to 1 week, or frozen (wrapped well) up to 1 month. Finished cake: best within 1–3 days. If refrigerated, let it sit 20–30 minutes before serving for the smoothest buttercream texture.