Preheat oven to 350°F. Place hazelnuts in single layer on rimmed baking sheet and roast in oven until light golden brown, about 10 minutes. Remove from oven and let cool until warm enough to handle without getting burned. Rub skins off hazelnuts.
Place 1/2 cup hazelnuts in bowl of food processor; pulse until finely chopped. Add 1/2 teaspoon cinnamon, flour, 1 cup butter, 1/2 cup granulated sugar and 1/4 teaspoon salt. Pulse until dough comes together when pressed.
Line 9-inch square baking pan with foil (with edges hanging off) and butter. Press dough into bottom of pan in even layer. Bake until golden brown and firm, about 40 to 45 minutes.
Meanwhile, roughly chop remaining hazelnuts; set aside. In medium saucepan, combine remaining 1/4 teaspoon cinnamon, 3 tablespoons butter, 1/4 cup granulated sugar, 1/4 teaspoon salt, honey and brown sugar. Set over medium heat and bring to boil, stirring often. Remove from heat and stir in reserved hazelnuts. Pour over baked crust and spread evenly to cover completely. Roughly chop dark chocolate chips and sprinkle over top of bars.
Bake until set, about 18 minutes. Let cool completely on wire rack. Lift bars from baking pan, using excess foil paper and cut into 16 squares and then cut in half diagonally. Store bars in airtight container in refrigerator.