Preheat oven to 350 F. Crush shelled and roasted nuts to smaller chunks. If they aren't shelled and roasted you can shell, lay on baking sheet and roast for 12 minutes until lightly browned, then crush when cooled.
Coarsely chop roasted hazelnuts, set aside 1⁄2 cup. In small saucepan, melt 2 tbsp of your butter. Combine melted butter and remaining hazelnuts in a small bowl. Set aside.
In medium bowl, cream 7 tbsp butter, sugar, egg, and vanilla until fluffy. Stir in hazelnut and butter mixture. Set aside.
In another small bowl, combine flour, baking soda, and salt. Add flour mixture to butter mixture filled bowl. Stir to combine and then add in remaining hazelnuts. Stir in white chocolate chips and 1/4 c of your semi sweet.
Use a small cookie scoop or spoon to place cookies on a parchment lined baking sheet. Bake 10 minutes or until lightly browned on edges and middle is not longer wet. Place cookies on a wire rack (on sheet, do not remove) to cool.
Melt remaining semi sweet in microwave in 30 second increments until smooth, drizzle over the top of cookies.