Line a sheet pan with parchment paper.  Preheat the oven to 400 F.

In a food processor, add the pecans, egg whites, and sugar and pulse until paste-like.  Set aside.

Slice the peaches.  Cut the peaches in half around the seed, twist the halves to separate from the seed.  If the peach pits are not cooperating, slice the halves away from the pit. Place flat side down on the cutting board and slice.  Keep the sliced halves together on the cutting – this will make it easier to arrange the slices nicely.

Lay the puff pastry out on the prepared sheet pan.  Spread the pecan paste, leaving a 1 inch boarder around the perimeter.  Fan out the peach slices and lay them on top of the pecan paste.  Completely cover the paste layer.  It’s ok to overlap the peaches somewhat.

Fold the edges up and over to contain the tart filling.

In a microwave-safe cup, melt the butter and honey together.  Stir.  Drizzle this mixture over the peaches.  You may want to use a pastry brush to evenly distribute.

Add about 1 tablespoon of water to the egg yolk and whisk with a fork.  Use a pastry brush to apply the yolk mixture to the visible puff pastry.  Sprinkle the puff pastry and tart all over with demerara sugar.

Bake the tart for 20-30 minutes or until the bottom of the pastry is golden brown.  The filling will look wet when it first comes out of the oven.  Allow the tart to cool for 10-15 minutes.  The filling will thicken so that it is sliceable.  Enjoy warm or at room temperature with whip cream or sweetened creme fraiche (optional).