Preheat oven to 350°F. In a large bowl, beat the butter, sugar and lemon zest with an electric mixer until light and fluffy. Add the egg yolks, vanilla, and salt; beat to combine. Beat in the lemon juice. Gradually add the flour, mixing until just combined.
Form the dough into walnut size balls and place them on parchment-lined baking sheets, two inches apart, pressing down to flatten. Bake until lightly golden, 12 to 13 minutes. Let cookies cool on the baking sheets for 5 minutes. Transfer to racks to cool completely.
Mix jam and berries into ice cream. Fill each with about 2 Tbs. ice cream; sandwich together. Wrap tightly in plastic. Freeze for 2 hours or more before serving.
