Pistachio Frosting Recipe

Ingredients (6)

• 5 1/2 ounces egg yolk (shy 2/3 cup; 155g), from about 10 large eggs
• 5 1/4 ounces plain or lightly toasted sugar (about 3/4 cup; 145g); see note
• 1 ounce liqueur or amaro, such as Cardamaro, Maraschino, and rum, or just water (about 2 tablespoons; 30g)
• 1/2 teaspoon (2g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight, or more to taste
• 16 ounces unsalted butter (4 sticks; 455g), softened to about 65°F (18°C)
• Homemade pistachio paste to taste, up to 14 ounces (396g)