• In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
• In a large bowl, whisk together the melted butter, brown sugar, and vanilla until uniformly mixed. Add the eggs, one at a time, whisking until they are incorporated. With a wooden spoon mix in the flour mixture all at once until just incorporated. It should be quite thick, but not dry. Add the chopped chocolate and nut pieces.
• Line a baking sheet with parchment paper. Press together roughly shaped 4.25-ounce (120g) dough balls. Don’t flatten them; the dough balls should be the shape of a baseball. Refrigerate the dough balls on the prepared baking sheet for at least 1 hour; if you have the time, the cookies will be even thicker if you let them sit for 24 to 36 hours. After they are chilled, you can bake them or freeze the dough balls for baking later.

BAKING INSTRUCTIONS

• Preheat the oven to 375°F/190°C convection heat (or 400°F/205°C flat heat). Double up two baking sheets and line with parchment paper. The double sheets will prevent the bottoms from over-browning in the hot oven. Evenly space six chilled dough balls on the prepared doubled baking sheets. Leave 2 inches/5 centimeters between them so they can be smashed after baking. Bake, one sheet at a time, in the middle of the oven for about 12 to 14 minutes or until they are golden brown on the outside, but still soft in the center.
• Remove the sheets from the oven and while they are still hot, gently smash the cookies with a metal spatula so they are 1-inch/2.5 centimeters thick disks. Allow the cookies to cool for about 5 minutes on the baking sheets, then move to a cooling rack.
• Enjoy slightly warm or at room temperature.

VARIATION: BROWN BUTTER SMASH BLONDIES

• Replace the butter with brown butter and mix as directed above. Smash the dough into a 9 by 13-inch/24 by 36-centimeter pan, lined with a lightly greased parchment-paper sling. Bake at 375°F/190°C for about 12 minutes, or until the edges are golden brown. Allow to cool completely in the pan before removing and cutting.