Super easy to make, but you need to wait about 6 weeks before it's infused. So plan in advance! With the hazelnuts that are left, you can make the fudgiest hazelnut brownies.
Add 2 cups raw hazelnuts with skins, coarsely chopped,¾ cup vodkaand¾ cup cognac or brandy to a clean jar with a lid. Close tightly, shake a little to mix, place in a cool, dark place (like a kitchen cabinet) and let steep for 4 weeks. After that time, the mixture with be cloudy.
Scrape 1 vanilla bean and add both the seeds and pod to the hazelnuts, together with 1 teaspoon cocoa nibs if using. Let it steep for 2 more weeks.
Make a simple syrup by stirring ¼ cup sugar with ¼ cup water in a saucepan until the sugar dissolves. You can also add 2 teaspoons brown sugar for a caramel tone. Bring everything to a boil and remove from the heat. Let cool.
Have ready a colander and piece of cheesecloth. I use the drip coffee filters. Sieve the hazelnut mixture through it, letting it drip. Don't rush it. Discard the filters as they fill with the wet hazelnut powder. Your liquid will be clear, and you'll have most of your hazelnuts intact.
Once all the liquid is sieved, you can discard the hazelnuts, make hazelnut brownies (I highly recommend it), or use them for something else.
Add half of the simple syrup to the liqueur. Taste it. It will not be completely mellow but you will get a feeling if you want more sweetness. Add more of the syrup if you feel it needs it.
Transfer to a bottle, using a funnel, add the remaining scraped vanilla bean, close the bottle and keep with your other liqueurs.
Notes
Optional ingredients: Frangelico liqueur has different flavor tones, and you can play with adding cocoa nibs and brown sugar for a more complex beverage. Don't use too much brown sugar, or it will overpower the rest.