Makes 24 2-1/2 inch swirls.
1-1/2 cups finely chopped walnuts
1 cup brown sugar
Zest of 1 lemon (finely grated)
1/4 tsp kosher salt
1/4 tsp ground nutmeg
2 Tbsp agave nectar
2-3 Tbsp all-purpose flour
2 sheets (1 package) puff pastry, defrosted according to package directions
1 egg, beaten with 1 tsp of water
Preheat oven to 400°F. Line two rimmed baking sheets with Silpats (silicone mats) or cooking spray, and set aside.
In a small bowl, combine the chopped walnuts, brown sugar, lemon zest, salt, nutmeg and agave, and mix well.
On your countertop, sprinkle half of the flour. Unfold one sheet of puff pastry onto the floured surface. Pinch the seams closed with your fingertips, if necessary, and roll the pastry into a rectangle 1/4-inch thick.
Spread half of the brown sugar mixture on top of the dough, pressing lightly so the mixture adheres, and leaving a 1-inch margin all the way around. Starting on one of the long sides, roll the pastry like a jelly-roll. Paint the last inch with the egg wash, to seal it. Place the pastry on the sheet pan, and refrigerate while you form the second roll.
Repeat with the remaining sheet of puff pastry. Place the second pastry roll in the refrigerator for 15 minutes.
Remove both rolls from the refrigerator, and, using a very sharp knife, cut into 1/2-inch slices. Lay the slices flat on the baking sheets, leaving plenty of room between them. Paint the pastry with the remaining egg wash.
Place both sheets in the oven and bake at 400F for 16 minutes, or until the pastry is lightly browned and puffed. You might have to rotate the pans halfway through the baking time.
When the swirls are done, remove from the baking sheets to a cooling rack. Let them cool, then serve at room temperature. Puff pastry doesn't keep very well, but if you have leftovers and must keep them, make sure they are completely cooled and store in an airtight container.