Notes: To brown butter, place in an 8- to 10-inch frying pan over medium heat and cook until lightly browned, 5 to 10 minutes. Pour into a bowl; let cool to room temperature. To toast hazelnuts, place in a baking pan and bake in a 350° oven until golden under skins, 10 to 12 minutes. Pour nuts onto a towel and rub to remove loose skins, then lift nuts from towel (discard skins). When cool, whirl in a food processor until coarsely ground. Store cookies airtight for up to 3 days.