Pâte à Bombe Buttercream

Pâte à Bombe Buttercream: The Egg Yolk Method. A pâte à bombe base — hot sugar syrup beaten into egg yolks — creates a fundamentally different buttercream from either American (butter and icing sugar) or Swiss meringue (egg whites and sugar). The yolk-based method produces a lighter, silkier texture with a richness that nods to the egg-yolk-heavy pastry tradition of Portuguese convents, where nuns famously used surplus yolks (left over from starching habits with egg whites) to create pastéis de nata, ovos moles and countless other confections. The sugar syrup must reach exactly 116°C (240°F) — the soft-ball stage — before being drizzled in a thin stream into the beating yolks. Hitting the whisk will cause dangerous spattering, so aim for the side of the bowl. The mixture must then beat on high speed for a full 8–10 minutes until completely cool; adding butter to a warm base will melt it and produce a soupy, broken buttercream. If the buttercream does curdle when the butter goes in, keep beating — the curdled stage is a normal phase caused by the temperature difference, and continued beating will warm and emulsify everything into a silky finish.