*Be sure to use a high-quality chocolate as it will make a big difference in the final flavor. We used a mixture of extra dark and semi-sweet Valrhona chocolate
1. Preheat oven to 350° F.
2. Pulse flour, sugar, cocoa, and salt in a food processor until combined. Add butter, and pulse until mixture is coarse, about 10 seconds. Add yolks and vanilla, and process until mixture just begins to hold together (no longer than 30 seconds).
3. Shape dough into a disk. Wrap in plastic, and refrigerate until firm, at least 1 hour.
4. Roll out chilled dough to 1/4 inch thick and