Preheat the oven to 300°F (150°C). Line a large 9" x 13" baking sheet with parchment paper. Note 1
(Optional, but recommended) If you are using raw sesame seeds, toast them in a dry pan over medium heat for 3-6 minutes until fragrant. Set aside to cool. Also toast the walnuts (or any other nuts) in the pan until browned and fragrant, around 5 minutes. Roughly chop the walnuts and set aside to cool. Note 2
In a bowl, add the egg whites, sugar, and salt. Mix until just combined. Do not whisk or incorporate any air.
Add the sesame seeds and walnuts to the bowl. Mix well to combine.
Pour the mixture into the lined baking sheet. Press down firmly to make sure the candy is compact. Note 3
Bake the candy for 1 hour.
Remove the candy from the oven and use a sharp knife to cut it immediately into squares. The candy is easiest to cut when warm.
Let the candy cool before storing in an air-tight container. The sesame snack can be stored for up to a month in a cool, dry place.