Instructions

1. Place the butter, sugar, salt, and vanilla extract in a medium bowl, and using an electric hand mixer, beat the butter mixture for 3 minutes on medium speed until the mixture is creamy and smooth.
2. Add the all-purpose and hazelnut flours, and mix just until mixture comes together.
3. Dump mixture onto plastic wrap, and form into a 1/2 inch disc and refrigerate at least two hours. (The dough may be frozen for up to two months)
4. Remove from the refrigerator and let sit 10 minutes.
5. Sprinkle a clean counter lightly with flour, and roll dough out with a rolling pin to a thickness of 1/4 to 1/3 of an inch.
6. Use a round cookie cutter to cut out the cookies, placing them on a parchment covered baking sheet.
7. Place trays back into the refrigerator for 20 to 30 minutes.
8. Preheat oven to 325 degrees F.
9. Bake the cookies for 25 minutes rotating pans halfway, or until just golden brown.
10. Remove from the oven and using a spatula, carefully transfer cookies to a wire rack to cool completely.
11. To make the ganache, place the chopped chocolate in a bowl.
12. Heat the cream in a small pot over medium heat just until you see bubbles on the top.
13. Pour the cream over the chocolate and let sit like this for a minute or two, then begin stirring until the chocolate has completely melted and the ganache is very smooth.
    cool for an hour.
14. Use a pastry bag to pipe the ganache between in the center of one cookie, then place a second cookie on top, and gently press together.
15. Continually to sandwich pairs of cookies together with the chocolate ganache, then cool completely.
16. If using the chocolate drizzle, place the chocolate chips in a glass bowl and microwave until melted, stirring often until the chocolate is smooth.
17. Use a fork to drizzle the melted chocolate over the top of each of the cookie sandwiches.
18. Cool completely until chocolate is firm.
19. Store in an airtight container in a cool place.