Coarsely chop the hazelnuts, reserving some halves to decorate the scones. Likewise, chop the chocolate into small and large pieces, saving some of the larger pieces for decorating later.

In a large bowl, whisk together the flour, baking powder, salt, ground cinnamon, and brown sugar for about 30 seconds. Break up any large clumps of brown sugar with your fingers.

Grate the frozen butter directly into the dry mixture. Toss it gently with your fingers to coat it in flour.

Toss in the chopped hazelnuts and chocolate, mixing them with the butter and flour.

Make a well in the center of the mixture and add the heavy cream. Fold the dry ingredients into the cream using a silicone spatula until the dough comes together and feels slightly sticky.

Lightly flour your countertop and turn the dough out. Fold and press the dough about four times to ensure it holds together.

Shape the dough into an 8-inch circle and cut into 8 wedges. Top each scone with reserved chocolate pieces and hazelnuts. Chill in the fridge for at least 30 minutes or up to 24 hours.

Preheat the oven and brush the tops of the scones with egg wash. Bake until golden brown and enjoy the aroma filling your kitchen.