Scoop 12 mounds of the chocolate hazelnut spread, about 1 tablespoon each, onto a parchment-lined plate. Freeze for 1 hour until solid.
In a medium bowl, whisk together the flour, cornstarch, baking soda and salt. Set aside.
In a large bowl, beat the dairy free butter, brown sugar and granulated sugar for 2 minutes until light and fluffy. Beat in the egg, egg yolk and vanilla until smooth.
Add the dry ingredients and mix on low speed just until combined, then fold in the chocolate chunks and hazelnuts. Cover and chill the dough for 30 minutes while the filling finishes freezing.
Preheat the oven to 350°F and line two baking sheets with parchment paper. Divide the dough into 12 equal portions, about 1/3 cup each, and flatten one portion in your palm.Set a frozen mound of filling in the center, wrap the dough around it and pinch to seal completely. Roll into a tall ball and repeat, placing 6 cookies on each sheet.
Bake for 12-14 minutes, until the edges are golden and the centers look soft. Let the cookies cool on the sheet for 10 minutes before serving, as the gooey centers are very hot.