- Preheat the oven to 375F (190C). Grease a 9-x-13-inch pan and line it with parchment paper so that the paper comes up the sides.
- Melt the chocolate and butter together over low heat, stirring until melted. Set aside to cool slightly while preparing the other ingredients.
- Whip the eggs and sugar using electric beaters or a stand mixer fitted with the whip attachment until the mixture holds a ribbon when the beaters are lifted, about 5 minutes.
- Pour the melted chocolate into the batter and whisk in by hand. Sift the flour, cocoa powder and salt overtop and fold in with a spatula until evenly combined. Scrape the batter into the prepared pan and spread to level it.
- Stir the peanut butter and dollop this over the brownies. Stir the jam to loosen it and dollop it on top. Use a butter knife to swirl the peanut butter and jam through the brownies; don’t be afraid to really pull it through the brownie batter, not just on the surface.
- Bake the brownies for about 30 minutes, until they begin to rise at the edges. Cool the brownies completely in their pan. Remove the brownies to a cutting board using the parchment paper and cut into squares.
The brownies will keep, well-wrapped and unrefrigerated, for up to 5 days.