Place hazelnuts on a small nonstick pan and roast on low heat until golden (about 10 minutes). Using a wooden spoon, keep moving them around so they don’t burn- and are evenly browned. Once the nuts are roasted, transfer them onto a clean dish towel, and cover them up. After 5 minutes, use a dish towel to rub the hazelnuts and remove as much of the skin as possible. Next, chop them finely.
As hazelnuts roast, to a small bowl add flour, cornstarch, baking soda, sugar, and salt. Combine the ingredients.
To a large bowl, add butter and use a handheld mixer to beat it until smooth (about 2 mins).
Now a few tablespoons at a time, add dry mix from the smaller bowl into the larger bowl. Use the mixer to incorporate the ingredients.
Add egg and vanilla into the bowl and incorporate using the mixer.
Add hazelnuts and chocolate chips. Incorporate these gently with a wooden spoon.
Line a baking sheet with aluminum foil or parchment paper.
Using your hands, create small consistent-sized balls of dough, place on cookie sheet and lightly press down. Leave space between each cookie to expand.
