1) In the top of a double boiler, whisk the sugar and egg yolks until the sugar has dissolved and the mixture is pale yellow, then whisk in the lemon juice and zest. Set the bowl over simmering water and whisk constantly until the mixture reaches 63C; it will visibly thicken but don't let it get too hot or the eggs will curdle.
2) Remove the bowl from the heat and add the rosemary and butter a little at a time, whisking until each addition is incorporated and the curd becomes thick. Transfer to a bowl, cool and then refrigerate until well chilled.
3) Divide the berries among six decorative bowls or glasses. Top with a dollop of the lemon curd and sprinkle with biscotti crumbs.
Cook's Note: Time of the year matters with rosemary. If you use rosemary in the winter, use half as much because it's stronger - it grows slower and the taste is concentrated.