1. Line a small baking sheet with wax paper. In a chilled bowl, using a hand-held electric mixer, beat the crème fraîche with the lemon curd and lemon zest until firm peaks form.
2. Arrange half of the cookies on the baking sheet and spoon the lemon cream onto the centers, letting it ooze gently to the edges. Top with the remaining cookies, pressing down very gently. Transfer the baking sheet to the freezer and freeze the sandwiches until firm, at least 4 hours.
3. Spread the nuts on a plate and roll the edges of the sandwiches in them. Serve at once.
Make Ahead: The lemon cream sandwiches can be frozen in an airtight container for up to 1 week.