In a medium bowl, whisk together 1 cup flour, ? teaspoon baking soda and ? teaspoon salt for the peanut butter cookie dough.

In the bowl of a stand mixer or using an electric hand mixer, beat 5 tablespoons butter, ? cup brown sugar and ? cup granulated sugar on medium-high speed until light and fluffy, about 2 minutes. Beat in ? egg until combined. Scrape down sides of the bowl, then beat in peanut butter and ? teaspoon vanilla until creamy. Stir in flour mixture until combined.

Turn out dough onto a lightly floured surface; roll into a ?-inch-thick rectangle. Wrap in plastic wrap; set aside.

In a medium bowl, whisk together 1 cup flour, ? teaspoon baking soda and ? teaspoon salt for the sugar cookie dough.

In the bowl of a stand mixer or using an electric hand mixer, beat 8 tablespoons butter and ? cup granulated sugar on medium-high speed until light and fluffy, about 2 minutes. Add ? egg and ? teaspoon vanilla; beat until just combined. Stir in flour mixture until just combined.

Turn out dough onto a lightly floured surface; roll into a ?-inch-thick rectangle. Wrap in plastic wrap. Freeze both doughs for 30 minutes.

In a medium bowl, whisk together cocoa powder, ? cup flour, ? teaspoon baking soda and ? teaspoon salt for the brownie batter.

Melt remaining 3 tablespoons butter; whisk with 6 tablespoons brown sugar until combined. Whisk in 1 egg and ? teaspoon vanilla until smooth. Fold dry mixture into wet mixture; stir until thick and smooth. Refrigerate for 15 minutes.

Generously flour two large pieces of parchment paper. Roll chilled peanut butter dough on one sheet to an 8?12-inch rectangle. Repeat with sugar cookie dough on the second piece of parchment. Layer sugar cookie dough on top of peanut butter dough, parchment side-up, and trim edges.

Spread brownie batter evenly on top of sugar cookie dough. Roll up the dough tightly using parchment and place seam side-down. Freeze until firm, about 30 minutes. Shape into a circle and cover in plastic wrap. Freeze until solid, at least 6 hours.

Preheat oven to 375?F; line 2 baking sheets with parchment paper.

Slice half of the frozen dough into six ?-inch slices. Place on lined baking sheet, spaced 2 inches apart. Bake until golden and just set, about 15-20 minutes. Cool on baking sheet for 15 minutes, then transfer to a cooling rack. Repeat with remaining dough.