Preheat the oven to 200 degrees C (400 degrees F). Place the hazelnuts on a baking tray and toast in the oven for about 8 minutes, or until fragrant. Remove from the oven and cool. When cool enough to handle, place the nuts on a kitchen towel, fold the towel over to cover them and rub to remove the skins.
Place the cooled hazelnuts into a food processor or blender and grind to a fine powder. Add 2 tablespoons of butter to the nuts and blend thoroughly. Set the hazelnut butter aside.
Melt 1 cup of butter in a small saucepan, and keep hot. In the container of a blender, combine the egg yolks, salt, pepper and lemon juice. Cover, leaving the hole in the lid open, and blend for about 5 seconds. Continue to blend at high speed while pouring butter in through the lid in a thin stream. Stir in the hazelnut butter while still warm. Keep warm until serving or serve immediately.