Preheat the oven to 350 degrees.
Grease 6-8 4 inch tart rings or a 9 inch springform pan. If using tart rings, place them on a baking sheet lined with parchment. If using a springform, line the bottom with parchment.
Spread the hazelnuts on a baking sheet and toast in the oven for 10 minutes or until fragrant.
Transfer the hazelnuts to a food processor and grind into a flour.
In the bowl of a stand mixer, fitted with the paddle attachment, cream the butter until light and fluffy. Scrape down the sides of the bowl, add the sugar, and continue beating.
Add the eggs one at a time, mixing until incorporated. Mix in the hazelnut flour and cornstarch.
Stir in the chopped chocolate and cranberries.
Spread the batter into the tart rings or springform pan and gently press whole cranberries into the top. Sprinkle with the turbinado sugar.
Bake for 30-40 minutes until slightly puffed and golden around the edges.