Blend the sea salt, brown sugar, rosemary, garlic, green onion, maple eau de vie and maple syrup together using an electric blender. Once blended spread the mixture over the trout fillets. Place the fillets on top of each other and cover with cling film. Let marinate for 24 hours
The next day, remove the fillets from the cling film and rinse under cold water. Slice the fillets thinly.