For the tart dough: Place the dry ingredients in a food processor and add the cold butter. Pulse until there are pea-sized crumbles.
Stream in the whole milk and egg yolk, pulsing again just until the mixture comes together. Do not overmix!
Turn the dough onto a clean surface and knead with your hands until smooth. Wrap in plastic and let chill for at least 1 hour.
Roll the dough into a 9- to 10-inch circle between two pieces of parchment or wax paper sprinkled with a bit of flour. Let chill again for 30 minutes more.
Brush the inside of an 8-inch tart mold with a little bit of olive oil. Peel away the top layer of paper, invert the crust into the mold, and fit it into pan. Press the edges so that they fit snugly in the corners of the pan.
Use a small knife or offset spatula to trim the excess dough and use a fork to poke the bottom a few dozen times before placing the shell in the freezer.
Heat oven to 325°F. Once your shell is frozen, bake for 10 to 15 minutes, until light golden brown, then let it cool completely.
For the hazelnut filling: In a medium bowl, whisk together the butter, sugar, corn syrup, vanilla, salt, eggs, half of the toasted hazelnuts, and half of the chocolate chips.
Pour the mixture into the baked shell. Sprinkle the rest of the hazelnuts and chocolate chips evenly on top.
Bake for 20 minutes, then rotate and bake for 10 minutes more, or until the center is firm and the hazelnuts are golden in color.