May want to give this site a look....I was just looking up online yesterday that best way to incorporate a hazelnut taste to a stout or porter
https://www.apexflavors.com/Beverag...-flavor-nut-free-beer-cider-wine-spirits~2180
Here's a HBT thread on it....
https://www.homebrewtalk.com/forum/...nut-oatmeal-cookie-who-has-experience.654715/
I used their toasted coconut flavoring on my current milk stout. It's perfect.