Roast 320 g of hazelnuts at 360 °F for 15 minutes. Let the nuts cool to room temperature. Remove the skins by rubbing the cooled down nuts in your hands until most of the skins have come off. Remove as much of the skins as possible off of the hazelnuts.
Place 100 g of roasted hazelnuts aside for later. 
Place the other 220 g of hazelnuts into a food processor.
Add 1 tbsp of granulated sugar.
Blend the hazelnuts on low, and then on high until the hazelnuts are a fine texture. They only need about 10-25 seconds of blending in total. You don't want to overdo it and make a paste.
Set aside the blended hazelnuts for later.
Using a hand mixer, beat the 8 egg whites, 1/3 cup sugar, 1/8 tsp cream of tartar, and a pinch of salt on high until the egg whites form stiff peaks. 
Using a spatula, gently fold in the blended hazelnuts and 1 2/3 cups icing sugar into the egg whites. Do not overmix. You want the egg whites to maintain the air you just beat into the egg whites.
 Chop the 100 g of roasted hazelnuts that you set aside.
Line a 12 x 16" pan with parchment paper.
Place the egg white mixture into the pan and spread evenly using a spatula. The mixture will not even out in the oven, so it's best to even it out as best you can before putting it in the oven.
 Place the chopped hazelnuts evenly around the hazelnut dacquoise.
Bake the hazelnut dacquoise for 20-22 minutes at 340 degrees F until the egg whites are a light brown color.
Let the dacquoise cool, then lift it out grabbing with the parchment paper at either end.  
 You can cut the dacquoise to fit your cake bottom. You can also freeze the rest of it if you don't use all of it with your recipe. Store in the freezer for up to 1 month.