In a medium saucepan over medium heat, combine raspberries, sugar, water, and cornstarch. Mash the berries gently as they warm, stirring frequently for about 10–15 minutes until the mixture thickens and bubbles. Once thickened, remove from heat and allow the jam to cool completely before using in your Vegan Jam Tarts.

In a large mixing bowl or food processor, combine all-purpose flour, vegan block butter, and powdered sugar. Mix until the mixture resembles breadcrumbs, then add cold water gradually, mixing until a pliable dough forms, around 2–3 minutes. If necessary, adjust the consistency with additional flour or water, ensuring the dough is smooth and not sticky.

Lightly flour your work surface and roll out the dough to about 5 mm thick. Using a round cookie cutter or a glass, cut out circles that will fit into your tart molds. Gather any excess dough, re-roll, and continue cutting until you have enough pastry circles for all your Vegan Jam Tarts.

Preheat your oven to 180°C (350°F). Grease your tart tins with a little vegan butter. Carefully press each pastry circle into the tins, ensuring they fit snugly. Spoon the cooled jam into each pastry shell, filling them generously but leaving a little space at the top. Smooth the surface of the jam for an even finish.

Place the assembled Vegan Jam Tarts in the preheated oven and bake for approximately 20 minutes, or until the pastry is golden brown and flaky. Keep an eye on them towards the end of baking, as the time may vary depending on the oven.

Once baked, remove the tarts from the oven and let them cool in the pans for about 10 minutes. Gently remove the tarts from the molds and transfer them to a wire rack to cool completely. Serve them warm or at room temperature, and enjoy the delightful flavors of your Vegan Jam Tarts!