01 -
Melt chopped bittersweet chocolate with butter and heavy cream in a small saucepan over low heat, stirring until glossy. Whisk in cocoa powder to thicken. Pour into a shallow dish and refrigerate until firm, at least 4 hours.
02 -
Beat softened butter with brown sugar and granulated sugar until pale and fluffy. Mix in the egg and vanilla extract. Fold in the flour, cocoa powder, baking soda, and salt until just combined. Cover and chill for 2 hours.
03 -
Scoop teaspoon-sized portions of the cold fudge and roll them in cocoa powder to coat. Place on a parchment-lined plate and freeze for 30 minutes until firm.
04 -
Scoop the dough into 14 balls. Flatten one ball into a disk in your palm. Place a frozen fudge ball in the center and wrap the dough around it, pinching to seal completely. Roll gently, place on a tray, and refrigerate the stuffed balls for 15 minutes while the oven preheats to 375 degrees F.
05 -
Arrange the chilled dough balls 3 inches apart on parchment-lined baking sheets. Bake for 8 to 10 minutes until the edges are set and the tops look matte and slightly crackled. The centers should still feel soft. Cool completely on the baking sheet.
06 -
Let the cookies cool on the baking sheet. Serve warm for a molten center, or at room temperature for a firm, fudgy core.