Pre-heat oven at 350 degrees. When oven is ready, place hazelnuts in sheet pan, and place pan in oven to toast the hazelnuts for about 10-15 minutes, or until hazelnuts are fragrant.
In a large glass bowl (or an other microwave-safe bowl), combine the marshmallows and butter. Once melted, take bowl and then mix with spatula. Depending on how strong your microwave is, this could take anywhere from 1-2 mins. I usually work in 30 second increments.
Add in milk chocolate chips, and semi-sweet chocolate chips, and microwave until melted. Mix again until chocolate is evenly distributed in the mixture, and it's a deep brown color.
Add in hazelnuts and liqueur or vanilla extract to bowl with melted ingredients, and mix one more time.
Get two wafer sheets ready, and working quickly, pour ingredients from the bowl over one of the wafer sheets, and spread mixture until the wafer sheet is covered.
Put other wafer sheet on top to enclose the mixture. Then, place a sheet of parchment paper on the top wafer sheet, and weigh down with something heavy (e.g. books or something to press down), and leave weight on for 30 minutes.
After thirty minutes, check to see if wafers are sealed, and once ready, cut into diamond shapes. Serve and enjoy, or store in freezer for later!