Start by placing the creamy conventional peanut butter in a heat-safe bowl. Microwave it for 20-30 seconds until it becomes pourable. Carefully spread the melted peanut butter in an even layer across the bottom of a lined 8-inch square pan. Pop it into the freezer for about 1 hour.

Preheat your oven to 350°F (175°C) to ensure it’s hot when the brownies are ready to go in. In a microwave-safe bowl, combine the unsalted butter and semisweet baking chocolate. Melt them together in 30-second bursts, stirring in between each burst, until fully combined and smooth. Allow this mixture to cool slightly.

Once the chocolate mixture has cooled down, add in the granulated sugar and whisk until the mixture is glossy. Next, crack in the eggs one at a time, along with the vanilla extract, stirring to incorporate thoroughly. Gradually fold in the all-purpose flour, unsweetened cocoa powder, and fine sea salt until everything is combined.

Pour half of the brownie batter into your prepared pan, spreading it evenly. Carefully lift the frozen peanut butter layer from the freezer and place it on top of the brownie batter. Pour the remaining brownie batter over the peanut butter layer, ensuring it’s fully covered.

Slide your assembled brownies into the preheated oven and bake for about 30 minutes. They’re ready when the edges look firm and a toothpick inserted into the center comes out slightly gooey.

Let your brownies cool in the pan for about 30 minutes. Carefully lift them out using the parchment paper, and allow them to cool completely on a wire rack for another 30 minutes before slicing.