Preheat oven to 375°. Spread hazelnuts on a baking sheet and bake until toasted and fragrant, about 10 minutes. Wrap toasted nuts in a cloth and rub to remove as much skin as possible. Let cool. Transfer to a food processor and pulse until nuts resemble coarse cornmeal.
Break pork into small chunks and put in a large bowl. Sprinkle ground hazelnuts, parsley, hazelnut liqueur, honey, salt, pepper, and mace over the pork. Using your hands, gently mix all ingredients together.
To check seasoning, cook a small amount of sausage in a frying pan over medium-high heat until browned and cooked through. Taste, then season pork mixture with more salt or pepper as desired.
Scoop out 1/4-cup portions of sausage mixture and form into 3-in.-wide patties. Working in batches, cook patties in a large frying pan over medium-high heat until brown on one side, about 3 minutes. Flip patties, reduce heat to medium-low, partially cover, and fry until cooked through, about 5 minutes.