These slice and bake cookies can be made ahead and then sliced and baked from frozen. It's a great dough to keep in the freezer and then bake a few cookies at a time when you're in the mood for something sweet.
Preheat the oven to 350 degrees and then toast the pecans for 7-9 minutes or until they start to smell toasted and look slightly golden. Using a food processor grind the hazelnuts with a couple spoonfuls of the flour until the nuts are in small pieces. A few larger pieces is fine but we want them to be mostly quite small.
Combine the flour, ground nuts, baking powder, and salt in a small bowl and set aside
Cream together both sugars and the butter. Once light and fluffy add the eggs and vanilla and beat until combined.
Add the flour and chopped chocolate mixture to the butter and mix slowly until just combined.
Pour the mixture onto a long piece of cling film and press into a log shape. Roll up in the cling film and roll a couple times on the counter to shape the dough into a log. Refrigerate for at least 2 hours or freeze until ready to use.
When you're ready to bake the cookies, preheat the oven to 350 and line a baking tray with a silicon mat or parchment paper.
Slice the log into cookies that are 1/4 -1/2 inch thick and lay them on the cookie sheet.
Bake for 10-12 minutes or until the edges have started to turn a nice golden brown but the middle is still pale. Let them cool for 10 minutes before removing them from the baking sheet.