Working with one mold at a time, spoon in a few tbsp. ice cream. With bottom of a fat-handled wooden spoon, pestle, or cocktail muddler, gently tamp ice cream even. Top with a few spoonfuls of sorbet; tamp even.
Repeat layers, alternating ice cream and sorbet, until mold is filled. Top with lid and freeze. Repeat with remaining molds and freeze until pops are firm, at least 2 hours.
*If ice cream is airy, you may need as much as 3 1/2 cups, because it will collapse when measured.
Make ahead: Up to 2 months.