Dissolve the yeast in the warm water with the maple syrup or sugar and let stand for about 10 minutes until foamy.
In a stand mixer bowl or large bowl, combine the flour, yeast mixture, walnuts and salt. Use a dough hook attachment or mix by hand until the dough is well-combined. If using the dough hook, allow it to knead the dough until smooth.
Transfer the dough to a lightly floured surface and knead until smooth and elastic (some of the walnuts may fall out in the process, but just fold them back into the dough).
Place the dough in a lightly oiled bowl, cover with plastic and let rise for 1 hour until doubled.
Punch the dough down and divide into 12 even pieces. Shape each piece into a ball and place on a parchment-lined baking sheet. Flatten the balls slightly with the palm of your hand.
Carefully cover the pan with plastic and place in a refrigerator overnight.
Remove the pan from refrigeration and allow the rolls to sit out at room temperature for about an hour or until slightly puffed.
Preheat your oven to 500°. Place a baking sheet or stone in the oven to preheat.
Whisk the egg white with a tablespoon of water. Uncover the rolls and brush each with a little of the egg white using a pastry brush.
Once your baking sheet or stone is hot, carefully transfer the rolls on their parchment into the oven, placing on the baking sheet or stone. Spritz the rolls with water using a spray bottle and quickly close the oven door to create steam.
Bake the rolls for about 10 minutes until they are nicely crisped and golden brown. Remove from the oven and cool completely.