Preheat the oven to 175° C and prepare two baking sheets.
Cream the butter with the sugars in a medium mixing bowl until nice and fluffy.
Mix together the vanilla with the coffee powder in a little bowl so the coffee powder dissolves.
Add the coffee vanilla mix and the applesauce to the creamed butter and sugar. Mix until combined.
Using a large sieve, add in the cocoa powder, flour, baking soda, and salt in a smaller mixing bowl.
Add the dry ingredients to the wet. Mix until combined. In the beginning it will seem to be a bit dry but once the ingredients are combined it will be the perfect texture. Mix only until just combined, do not overmix the cookie dough.
Spoon out the cookie dough in round dough balls. Then press a bit of a dent into each cookie.
Fill the dent with chocolate hazelnut butter.
Sprinkle chopped roasted hazelnuts on top of each cookie. Press slightly if the nuts aren't grasping onto the chocolate hazelnut butter.
Bake the cookies one sheet at a time for about 10 minutes. This depends on your oven, but the cookies are ready once the edges are set and the middle should look very soft. The cookies will continue to bake on the cookie sheets once they are out of the oven.
Sprinkle the cookies with a bit of flakey sea salt when they're out of the oven.
Store the cookies in an airtight container, and they are best enjoyed within a few days. Enjoy!
