Preheat your oven to 375°F.
Start by creating the pumpkin frangipane. In the bowl of a stand mixer, mix together the almond meal, powdered sugar, and cornstarch using the paddle attachment.
Add in the almond extract, butter, and pumpkin puree and mix on medium to medium high speed until well combined and fluffy. Scrape down the bowl as you go to make sure that everything is well incorporated.
Place your thawed puff pastry on a piece of parchment paper and roll it out slightly so it forms a larger rectangle. You don’t have to be too precise with this!
Cut the corners off of the top and another triangle from the bottom edge.
Use a spatula to spread a 3 inch wide layer of frangipane across the middle of the pastry. I used about ½ cup of the frangipane, but you can use as much or as little as you’d like! Just set aside ¼ cup of the mixture.
Use a pizza cutter to slice an equal number of thin diagonal lines into either side of the pastry.
Fold the top of the pastry down and then overlap strips of the pastry in an alternating pattern, similar to a braid.
Mix 1 tbsp of milk into the reserved ¼ cup of frangipane and spread across the top of the pastry.
Sprinkle on chopped pistachios and bake for 15-20 minutes, or until the pastry is golden brown and puffy.
Allow to cool on the pan for 10 minutes before transferring to a wire rack.
Dust with powdered sugar and slice before serving.