To make the cinnamon pastry, put the softened butter in a bowl, sift in the icing sugar and then add the ground almonds. Beat the mixture together until it becomes creamy.
Add the egg and beat the mixture until the egg is incorporated, sift in the flour, cinnamon and pinch of salt and stir until the dough comes together and forms a ball.
Shape the dough into a rectangle, wrap it in cling-film and place in the fridge for at least 2 hours. The pastry can be made a day or two in advance and just stored in the fridge.
Next make the creme diplomat, place the 2g of leaf gelatine in a bowl of cold water and allow it to soak.
Split the vanilla bean lengthwise and scrape out the seeds, place it in a saucepan with the milk, or add the vanilla extract to the milk.
Bring to a boil in a saucepan over a medium heat, then remove from the heat and let infuse for 10 minutes.
Meanwhile combine the sugar and flour in a medium bowl. Add the egg yolks and whisk just until the sugar and flour is combined, do not let it get too pale.
Whisk a third of the milk into the egg mixture to loosen it. Whisk in the remaining milk and return the mixture to the saucepan, straining it through a fine sieve. Cook over a medium heat, whisking constantly.
As soon as the pastry cream begins to thicken, lower the heat and cook out the flour for a couple of minutes, stirring continuously. Then squeeze the excess water out of the gelatine and add it to the creme patissiere you have just made, stir it until dissolved.
Scrape the pastry cream into a bowl and cover with a layer of clingfilm, pressing it down so it touches the surface of the cream. This will stop a skin forming. Allow to chill completely.
When the creme patissiere is cool, whip the double cream until it's semi-whipped.
Give the creme patissiere a stiff stir and then fold in the semi-whipped cream until fully combined. Place the creme diplomat in the fridge for at least 30 mins before using.
Grease the 12 tartlet tins with a little butter and place them on a baking tray(s).
Next roll out the pastry on a floured surface until around 3mm thick, using a pastry cutter, cut out 12 rounds to fill tartlet tins that are 7.5cm in diameter, pressing the pastry into the sides of the cases. Use a rolling pin to trim the excess pastry, by rolling it over the top of the case. Prick the base of the pastry with a fork a few times, repeat for the other 11 tartlets and then place the cases back in the fridge for 20mins to firm up before cooking.
Preheat the oven to 160C FAN, or 180C and cook the tartlets for 15minutes. The tartlets will shrink a little at the edges, but they do not need to be weighed down with baking beans etc, the holes in the base stop the pastry from puffing up.
Allow the cooked tartlets to cool on a rack before filling them to the edge with creme diplomat. Decorate the tartlets however you like with the blackberries.
Heat the jam with a tablespoon of a water in a saucepan and when it's turned to a syrup, use a pastry brush to coat the blackberries with jam to give them a glossy shine. Don't load the pastry brush with jam, just dab a little on at a time.