Preheat your oven to 425°F (220°C). This high temperature ensures that the outer layer of the cakes sets quickly, while the inside remains gooey.
Grease four ramekins with 1 tablespoon of the softened butter and dust with cocoa powder.
In a double boiler or microwave-safe bowl, combine the chopped German baking chocolate and 4 tablespoons of the unsalted butter. Heat gently until melted and smooth, stirring occasionally. Set aside to cool slightly.
In a separate bowl, whisk together the flour, cocoa powder, and a pinch of salt.
In another large mixing bowl, combine the granulated sugar and remaining softened butter. Beat with a whisk until creamy. Add the eggs, one at a time, mixing well after each addition.
Pour the melted chocolate mixture into the egg and sugar mixture, stirring gently until well combined.
Gradually add the flour and cocoa mixture to the chocolate batter. Use a spatula to fold the dry ingredients into the wet until just combined—be careful not to overmix!
Spoon the batter evenly into the prepared ramekins, filling each about halfway. Add a generous dollop of creamy peanut butter in the center of each ramekin, then cover with remaining batter until almost full.
Place the ramekins on a baking sheet and bake in the preheated oven for 12-14 minutes, or until the edges are firm but the center still looks soft.
Remove the ramekins from the oven and let them cool for 1-2 minutes. Carefully run a knife around the edges to loosen the cakes. Invert each ramekin onto a plate, give it a gentle tap, and lift off the ramekin to reveal the molten center. Dust with powdered sugar before serving.
