This Luxe, Goes-With-Everything Pistachio Frosting Will Forever Change You

For a Stand Mixer With a Bowl-Lift Design: Tear off a long strip of foil and crumple it into a thick ring. Place it in the bottom of a 3-quart saucier or similarly large, wide pot, and fill with roughly 1 1/2 inches water. Place over high heat until bubbling-hot, then adjust the temperature to maintain a gentle simmer. In a stainless steel stand mixer bowl, combine egg yolks, sugar, Cardamaro or other liquid ingredient, and salt. Place bowl over steaming water, stirring and scraping constantly with a flexible spatula, until egg yolk syrup reaches 155°F (68°C). This should take only about 5 minutes; if the process seems to be moving slowly, simply turn up the heat. Transfer bowl to a stand mixer fitted with a whisk attachment. For a Stand Mixer With a Tilt-Head Design: Fill a large pot with a few inches of water. Place over high heat until bubbling-hot. In a large heatproof glass or ceramic bowl, combine egg yolks, sugar, Cardamaro or other liquid ingredient, and salt. Set bowl over the steaming water, then cook, stirring and scraping constantly with a flexible spatula, until egg yolk syrup register 155°F (68°C); this should take no longer than 8 minutes; if the process seems to be moving slowly, simply turn up the heat. Scrape mixture into stand mixer bowl and fit stand mixer with a whisk attachment.

Whip the egg yolk mixture at high speed until fluffy, stiff, and beginning to ball up around the whisk, about 8 minutes. With mixer still running, add butter a few tablespoons at a time, waiting only a second or two between additions. In the end, the buttercream should be thick, creamy, and soft but not runny, around 72°F (22°C). When the consistency has been properly adjusted (see troubleshooting guide below), begin whipping in the pistachio paste a few tablespoons at a time, to achieve the desired intensity of flavor. Additionally, the buttercream can be seasoned with additional salt or other extracts to taste.

Use buttercream right away or transfer to a large zipper-lock bag, press out the air, and seal. Buttercream can be refrigerated for up to 2 weeks and frozen for up to several months. (The main issue with longer storage in the freezer is odor absorption, not spoilage.) Rewarm to 72°F and re-whip before using.

Troubleshooting: If warmer than 74°F (23°C), the buttercream will be soft and loose; pop it in the fridge for 15 minutes and re-whip to help it thicken and cool. If colder than 68°F (20°C), the buttercream will be firm and dense, making it difficult to spread over cakes and slow to melt on the tongue, creating a greasy mouthfeel. To warm, briefly set over a pan of steaming water, just until you see the edges melting slightly, then re-whip to help it soften and warm. French buttercream can be fixed according to the same rules for Swiss buttercream. For more information, see the troubleshooting guide and video here .