In a food processor pulse together flour, ½ cup of hazelnuts, salt and pumpkin pie spice; about 1 minute until finely ground. Transfer to a medium bowl.
In the processor pulse butter, powdered sugar and 1/8 cup creamer until smooth. Add flour mixture. Cover and process with pulses just until a dough forms, scraping sides as necessary. Add remaining ½ cup hazelnuts and pulse just until mixed in.
Divide dough in half and roll into two 8-inch rolls, about 1-½ inch thick. Wrap in plastic wrap and freeze 30 minutes to firm.
Preheat oven to 350º F. Unwrap cookie rolls and place on a cutting board. Slice into even pieces, about ¼-inch thick. Place slices onto a parchment lined baking sheet and bake 12–15 minutes, until edges are golden. Remove from oven and cool on wire rack.
In a small bowl mix together chocolate-hazelnut spread and about 2-tablespoons creamer to make filling. Spread desired amount to create a thin layer onto bottoms of half of cookies. Place reaming cookies bottom side down on filling to create shortbread sandwiches.
Notes
Adding flour to hazelnuts helps prevent it from forming into nut butter, but don't over-pulse
You can use any flavor sweetened creamer you'd like, but recommend pumpkin spice flavor if you can find it
Use softened or room temperature butter when mixing the dough to ensure it mixes evenly
Freezing prepared shortbread dough is a critical step as it makes it the right firmness for slicing and baking
Baked cookies can be stored in an airtight container for up to 1 week or stored in the freezer