These gooey, fudgy brownies are swirled with creamy peanut butter and fruity jam. Top them with crushed peanuts and a bit of sea salt for added texture. You won't believe how good these taste or how easy they are to make!
In a large heat-proof bowl, place chocolate and butter. Heat in the microwave in 20-30 second intervals, stirring in between each interval, until melted (or set it over a saucepan of simmering water, stirring occasionally). Add sugar to chocolate mixture and whisk until combined. Add eggs and whisk the mixture vigorously for several seconds until shiny. Add flour and salt and fold, using a rubber spatula, just until combined.
Pour batter into prepared pan and smooth the top. Heat the peanut butter for 10-15 seconds in the microwave so it's a more viscous consistency. Then, mix the jam to loosen it. If it's still too thick, microwave it for 10 seconds to loosen. Spoon alternating dollops of peanut butter and jelly on top of the brownies so it resembles a checkerboard. Using a knife or skewer, gently swirl together with the brownie batter to get a marble effect. Be careful not to over swirl and completely mix everything together. You want to still see lots of the peanut butter and jelly on top. If using, sprinkle crushed peanuts over the surface of the batter.
Bake for 25-28 minutes, until the edges are set but the center is still very soft. Be careful not to overbake. A toothpick inserted into the center of the brownies should come out with moist crumbs, not dry. Let brownies cool completely on a wire rack, then refrigerate until set for easy cutting. Lift brownies out of the pan using the parchment paper and cut into squares. Serve cold or at room temperature.
Store brownies in the fridge in an airtight container for up to 5 days. Brownies can be frozen for up to 2 months. Thaw them overnight in the fridge.