CHOCOLATE SWEET PASTRY

1. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until combined. Add the egg, and mix until incorporated. Add the vanilla bean paste and salt. In a medium bowl, sift together the cocoa and flour, and add to the mixing bowl. Mix until just combined.
2. Turn the dough out onto a piece of plastic wrap, and form into a rough rectangle. Wrap in the plastic wrap, and chill until firm, 3-4 hours, or overnight.
3. Lightly flour a work surface. Divide the dough into two pieces, and re-wrap the first piece until needed. Place the second piece onto a lightly floured piece of parchment paper. I made six shells at a time, so just worked with one piece of dough, but if you are making 12 at once, you can roll both out at once. Roll out to 3mm thickness, adding additional flour onto the dough as needed to prevent sticking. Once the dough is the correct thickness, transfer to the freezer for 5-10 minutes to firm up - you don’t want it to be solid, but want it cold enough that it doesn’t get sticky when you use it.
4. Line a baking sheet with a perforated baking mat or parchment paper. Remove the chilled dough from the freezer, and use your tart ring to cut out circles from the dough - these will form the bottoms of your pastry cases. Try and keep all the circles condensed in one part of the dough so you have enough left to make strips to form the sides of the shells - you can re-roll if needed. Place the stamped out circles inside the tart ring on the prepared baking sheet.
5. Now you need to cut strips to form the walls - you want to cut a strip that goes around the whole ring, so if you have a 3” ring, your strip will need to be just over 9” to accomodate the circumference. Cut strips that are about 9” long, and about ¾” thick. Place them inside the tart ring, trimming the length if needed so the ends of the strips sit flush, and pressing down lightly where the edge and the bottom meet. Repeat with the remainder of the tart rings. Chill for 5 minutes, then use a sharp knife to trim off any excess dough that sticks out over the top of the ring.
6. Transfer the lined tart rings to the freezer for 30 minutes to an hour, in order for them to firm up completely. While they are freezing, preheat the oven to 350°f / 180°c. Once the pastry cases are frozen, transfer the baking sheet to the oven. Bake the pastry cases for 15-16 minutes, or until set. In the first few minutes of the baking, check on them to ensure that the edges are not slipping down - if they are, just gently use your hands to bring them back up.
7. Remove the pastry cases from the oven, and allow to cool on the tray for 5-10 minutes, then carefully remove the cases from the rings, and place onto a wire rack to cool completely.
8. If you have just made six shells, repeat the process to give you 12. If you are making these ahead of time, you can store them in an airtight container at room temperature until ready to use. If the edges are a little rough, they can be filed down with a microplane.

DARK CHOCOLATE PEANUT BUTTER FILLING

1. Place the chocolate, peanut butter, butter and salt into a large heatproof bowl. Place the cream in a small saucepan, and warm over low heat until just shy of a simmer - you should see movement around the edges of the cream. Immediately pour the cream over the chocolate and butter, and cover the bowl with a lid or plate. Leave to sit for 5-6 minutes, then whisk vigorously to combine. The mixture will look like it has split to begin with but keep whisking - it will come together and go glossy. Use immediately.

ASSEMBLY

1. Arrange the chocolate pastry cases on a baking sheet. Dollop 2 tsp of mixed berry jam into the bottom of each, smoothing down with an offset spatula if needed.
2. Fill each pastry case with the chocolate peanut butter filling, shaking the pastry case slightly to level off the mixture, and smoothing with an offset spatula if needed. Repeat until all are full and smooth, then place in the fridge until set, 30 to 60 minutes.

SWISS MERINGUE

1. Measure the egg whites, granulated sugar and vanilla bean paste into the bowl of a stand mixer or other heatproof bowl. Place over a pot of simmering water, ensuring that the water does not touch the bottom of the bowl. Heat the mixture, whisking often and watching the edges carefully, until it no longer feels gritty when rubbed between your fingers, and it registers at least 70˚c / 160˚f on a thermometer. 
2. Carefully transfer to a stand mixer fitted with the whisk attachment. Whip on high speed until stiff peaks form, approximately 5-6 minutes. Transfer to a piping bag fitted with a french star tip (I used an ateco #866)
3. Pipe blobs of the swiss meringue onto the top of each tart - I only did a few on each because I liked how it looked, but they would look great totally covered in meringue too. You could also use an offset spatula, dollop it on, then smooth it off. Torch if desired.
4. Store the tarts in the fridge until ready to serve.