- Scoop the avocado flesh into a medium bowl and mash until mostly smooth. Add the lemon juice, hearts of palm, salt, and pepper.
- Spread the avocado mixture on 4 bread slices. Sprinkle with parsley and top with radish slices. Cover each with another piece of bread.
- Use a bread knife to cut the crusts off each sandwich, then slice each sandwich into four triangles or squares. Serve immediately or refrigerate the sandwiches in an airtight container for up to 3 hours before serving.