Makes about 1 ½ cups
1 to 2 (6-ounce) containers fresh raspberries, as needed
2 large egg yolks
2 large whole eggs
2/3 cup sugar
2 tablespoons freshly squeezed lemon juice
8 tablespoons (1 stick) unsalted butter, cold and cut into 8 pieces
2 teaspoons rose syrup or ½ teaspoon rose water
1. Place a fine mesh strainer over a larger mixing bowl. Place half the raspberries in the strainer and, using a spatula, push the berries through the strainer, pressing on the solids to extract as much puree as possible. You should have about ½ cup puree. If your berries are less juicy, you will need more; press additional berries through the strainer if necessary.
2. In a large bowl, whisk together the egg yolks and eggs. Whisk in the puree, sugar, and lemon juice. Transfer to a large saucepan. Place pan over medium heat and, stirring constantly with a heatproof spatula (make sure to stir the bottom and edges of the pot), cook until the mixture thickens, about 5 to 10 minutes. Do not let it come to a boil.
3. Remove from heat immediately and pour through a fine-mesh strainer into a bowl. Whisk in the butter, 1 tablespoon at a time, until smooth. Whisk in the rose syrup. Let cool 5 minutes, then transfer mixture to a small container and cover the surface with plastic wrap to prevent a skin from forming. Refrigerate until thoroughly chilled.