Ingredients (makes 16 cookies)

• 425 grams bittersweet chocolate, rough chopped, divided
• 57 grams unsalted butter, very soft
• 3/4 cup granulated sugar
• 1/4 tsp Salt
• 2 Large Eggs
• 2 tsp vanilla extract
• 3/4 cup all purpose flour
• 1/2 tsp baking powder
• 24 chocolate wafer biscuits (see note), broken into pieces
• 1/3 cup lightly toasted hazelnuts, chopped (optional)

Method

1. Adjust racks to upper and lower middle position and preheat oven to 190 degrees.
2. Melt 227 grams of the chocolate in a medium bowl over a pan of barely simmering water. Let cool slightly.
3. Line 2 baking sheets with baking paper. Whisk butter, sugar, and salt in a large bowl until combined. Whisk in eggs and vanilla. Whisk in chocolate until combined and glossy.
4. Stir flour and baking powder in a small bowl then stir into chocolate mixture until combined. Stir in remaining chocolate, chocolate wafer cookies (see note), and hazelnuts (if using). Chill until firm enough to scoop, about 15 minutes.
5. Using a 1/3 cup scoop, portion dough onto pans, spacing at least 2 inches apart. Bake until cookies are puffed, cracked, and almost set (centers may still look underdone), 12 to 15 minutes.
6. Let cookies cool on pan for 1 minute, then slide cookies (with paper) onto wire rack to cool.

Notes

I used Oreo cookies with the filling scraped out, but Nabisco Famous Wafers are my first choice. Instead of folding in all of the remaining chopped chocolate, you can set aside some of it to press into the tops of the dough balls just before baking.