Preheat the oven to 375 degrees F.  Using a small teaspoon, take each nectarine half and scrape away any pith from where the pit was removed.
Put the cookies into the bowl of a food processor and pulse to make small crumbs.  Place the cookie crumbs into a small bowl, add the liqueur, and mix with a fork.  Fill the nectarine halves with the mixture and place in an oven-proof dish.  Bake for 15 to 20 minutes.
Press the raspberries through a fine sieve to remove the seeds.  Heat the resulting juice in a small saucepan and stir in the sugar; simmer over medium heat for 7 minutes, or until the sauce has thickened.  Drizzle a little raspberry sauce on each plate and place 2 nectarine halves on top.  Serve.