Step 1

FOR THE FILLING: Combine peanut butter, sugar, and salt in bowl. Using fork or your hands, stir and mash mixture until thoroughly combined and no dry pockets of sugar remain. Divide filling into 16 equal portions (about 2 teaspoons each). Roll each portion into ball and place on large plate. Freeze until firm, about 30 minutes.

Step 2

FOR THE DOUGH: Meanwhile, adjust oven racks to upper-middle and lower-middle positions and heat oven to 300 degrees. Line 2 rimmed baking sheets with parchment paper.

Step 3

Whisk flour, cocoa, baking powder, baking soda, and salt together in medium bowl. Microwave 6 ounces (170 grams) chocolate, oil, and butter in second medium bowl at 50 percent power, stirring occasionally, until melted, about 3 minutes. Whisk vanilla into melted chocolate mixture until combined.

Step 4

Whisk 1 cup granulated sugar and eggs in large bowl until thoroughly combined. Add melted chocolate mixture and whisk until uniform. Using rubber spatula, fold in flour mixture until combined. Fold in remaining 4 ounces (113 grams) chocolate.

Step 5

Divide dough into 16 equal portions, about scant 3 tablespoons (1⅞ ounces or 53 grams) each; divide any remaining dough evenly among portions. Use your fingers to flatten 1 dough portion into disk with roughly 3-inch diameter. Place 1 ball of filling in center of disk. Wrap edges of dough up and around filling, seal dough, and shape into smooth ball. Repeat with remaining dough portions and filling.

Step 6

Place confectioners' sugar and remaining ⅓ cup granulated sugar in 2 separate shallow dishes. Working in batches, roll dough balls first in granulated sugar, then in confectioners' sugar, to coat. Evenly space dough balls on prepared sheets, 8 dough balls per sheet.

Step 7

Using bottom of drinking glass, flatten dough balls into 2-inch-wide disks. (Dough balls will crack at edges; this is OK. If filling shows through any large cracks, pinch dough together to seal cracks.) Bake until cookies are puffed, edges are just set, and cookies no longer look raw between cracks, about 22 minutes, switching and rotating sheets halfway through baking.

Step 8

Let cookies cool completely on sheets, about 30 minutes. Serve.