Fit a disposable piping bag with a #4 plain piping tip. Put the piping bag inside a container that will hold it standing up and open up the piping bag.
Pipe both frozen items simultaneously into the prepared piping bag so that there will be cassis sorbet on one side of the bag and almond ice cream on the other. Reserve the piping bag in the freezer for at least 45 minutes.
Set 10 macarons on a sheet pan, flat side up.
Pipe 30g / 1.06oz of the sorbet and ice cream on each macaron, and top with another macaron to form a sandwich. Work quickly.
Freeze immediately, using a blast freezer, if available; otherwise, place the sheet pan with the macarons directly underneath the freezer’s fan.
Once the frozen items have firmed up, transfer them to the middle or bottom of the freezer for service. Reserve in an airtight container. Temper the sandwiches for 4 to 5 minutes before serving.