Line a mini-muffin tin with paper liners.: The liners should fit snugly and create tidy cups, and you will feel the slight resistance when pressing them into each well, which helps keep the shells uniform. Make sure the tin is clean and dry, as any moisture can cause the chocolate to seize. A common mistake is using too thin liners that collapse when you spoon in melted chocolate, so choose sturdy mini liners for best results.
In a medium saucepan, combine the peanut butter, butter and sugar over medium heat. Stir constantly until completely melted and starting to bubble. Remove from the heat and add the powdered sugar, 1/3 cup at a time, stir after each addition until completely combined. Set aside and let the mixture cool.: You will notice the mixture begin to melt into a cohesive glossy mass as the peanut butter and butter soften, and the aroma becomes warmly nutty. Stir constantly to prevent scorching on the bottom, and watch for tiny bubbles forming around the edges which signal readiness to remove from heat. If you stop stirring, the mixture can stick and burn, producing a bitter taste.
Place chocolate and butter in a microwave safe bowl and melt in the microwave in 30 seconds increments, until completely melted, stirring after each burst.: As you fold in the powdered sugar, the texture will shift from runny to thick and malleable, and the sound will become quieter as the mixture thickens. Cooling is essential so the filling firms slightly, which prevents it from seeping into the chocolate shell. If you add the sugar too quickly the mixture can clump, so add it gradually and mix thoroughly for a smooth consistency.
Using a spoon, scoop a hefty spoon of melted chocolate into the bottom of each muffin liner.: The chocolate should transform into a glossy, velvety liquid and you will smell a toasty chocolate scent as the butter integrates. Stirring between bursts ensures even melting and reduces the risk of burning the chocolate. If you overheat even a little, the chocolate can seize and look grainy, so use short intervals and gentle stirring.
Using a spoon, scoop out the peanut butter mixture, roll into a ball and then flatten it slightly in your palm, place it on top of each chocolate lined muffin cup. The peanut butter shouldn’t touch the muffin tin walls. Refrigerate for 30 minutes.: As the chocolate spreads it will coat the base and you can tilt the tin slightly to encourage even coverage, watching for an even sheen and a thin rim where the chocolate meets the liner. Work quickly enough so the chocolate remains fluid, yet steady enough to avoid splashes. If the chocolate begins to thicken while you work, return it to gentle heat briefly to regain fluidity, taking care not to overheat.
In the bowl of an electric mixer fitted with the wire attachment, combine butter, salt and sugars until soft and creamy, about 2 minutes. Mix in the cream and vanilla seeds. On low speed add the flour and mix until combined. Using a spatula, stir in the chocolate chips. Make sure you scrape the sides of the bowl as needed during this step.: The filling should be pliable but firm enough to hold its shape, and pressing it gently into a flattened disc helps create a neat center that is fully encased by chocolate later. Keep the peanut butter away from liner edges to avoid unsightly seams and potential leaks. If the filling is too warm it will sag and touch the walls, so chill the pieces until firm.
Scoop the cookie dough onto the top of the muffin tin cups, until the tins are full. If the cookie dough sticks to your spoon, wet it in a little cold water. Pat the cookie dough on top in an even layer. Sprinkle any remaining peanut butter mixture or chocolate chips on top.: You will see the butter lighten and become airy, while the sugar becomes fully integrated, giving a pale, fluffy look. The vanilla seeds add tiny black flecks and a floral note that lifts sweetness. Folding in the all purpose flour and mini chocolate chips yields a tender dough; overmixing can develop gluten and make the dough tough, so stop as soon as combined.
Refrigerate for at least 5-6 hours or overnight before serving. Store in the fridge as the cookie dough becomes soft if kept too long at room temperature.: When you press the dough into place the surface should feel slightly cool and yield under light pressure, creating even domes. The contrast between the matte cookie dough and the glossy chocolate edge looks appealing. If you find uneven lumps, a wet fingertip or spatula smooths them quickly; avoid overworking the surface which can warm the dough.
Refrigerate for at least 5 to 6 hours or overnight before serving store in the fridge as the cookie dough becomes soft if kept too long at room temperature: As the cups chill the chocolate shell will firm to a satisfying snap while the interior sets to a scoopable, tender texture, and the aroma will mellow into a balanced peanut and chocolate harmony. Serving too soon yields a soft, unstable shell, while prolonged room temperature storage risks a softened filling. Keep them chilled and use a chilled serving plate for best results.