Preheat the oven to 325 degrees F.

Melt the bittersweet chocolate and butter in a double boiler over simmering water, stirring constantly.

Whisk together the sugar, eggs, vanilla extract, and salt in a large mixing bowl.

Sift together the flour and baking powder in a separate bowl.

Combine the chocolate, flour, and egg mixtures together.

Stir in the white chocolate and hazelnuts.

Rest the dough in the refrigerator until it begins to set up but is still soft enough to spoon out.

Drop 1 tablespoon portions of dough 2 inches apart on a parchment paper-lined sheet pan using 2 spoons.

Bake for 12 minutes.

Cool on the sheet pan for 10 minutes, then transfer to a wire rack to cool completely.