In a food processor, add hazelnuts and ¼ cup brown sugar and process until they are finely ground but not oily.

In a mixing bowl, add flour, baking soda, salt, and cinnamon and mix well. Set aside.

In a large bowl, add butter and remaining brown sugar and beat using a hand mixer until well combined. 

Add hazelnut mixture and beat until combined.

Mix in egg and vanilla extract. Add flour and mix until all ingredients are thoroughly combined.

Shape the dough into two balls, flatten out into a disk shape, and cover with plastic wrap. Refrigerate for 30 minutes to an hour.

Preheat oven to 400 degrees.

After chilling, take one ball of dough and roll it to ⅛ inch thickness, cut with a 2-inch cookie cutter, and add to the baking sheet. (These will be the bottom pieces).

Roll the second ball of dough to ⅛ inch thickness and cut with a cookie cutter, also cutting out the desired shape in the center with a mini cookie cutter (like the star). Place on another baking sheet. (These will be top pieces).

Cook for 4-5 minutes until the edges are golden brown. Move to a wire rack and allow the cookies to cool.

After cooling, lay top cookies on a tray and sprinkle with powdered sugar until evenly covered.

Spread ½ to 1 teaspoon of jam onto the bottom cookies and top with the top cookies.