In a pan, add the mixed berries, Ribena cordial, and water. Cook over medium heat for 3 – 5 mins until the mixture thickens.
Add in cornstarch. Stir constantly to ensure that the mixture is well mixed. To check if it is ready, use a spatula and draw a line in the middle of the pan. It is ready when the jam becomes a gel-like consistency and the line on the pan stays visible for a few seconds.
Switch off the flame. Set aside to let cool.
Step 2: Prepare the crumbles
Preheat the oven at 180oC.
In a baking dish, add flour, sugar, salt, cinnamon, and butter. Pinch the butter and mix it with the dry ingredients using your fingertips until you achieve a rough sandy and crumbly texture.
Transfer into the oven and bake for 15 mins.
Remove from the oven and let it cool down.
Use a spoon to break the crumbles into coarse grains.
Step 3: Assemble and bake
Preheat the oven at 180C, top heat.
Place the tart shells on the baking tray.
Add in Ribena berries jam to the brim and scatter the baked crumbles on top.
Transfer to the oven and bake it for 3 mins. Remove and ready to serve.