Prepare crust by adding buckwheat to a food processor and blending until fine and crumbly. Add in oats, dates, water and coconut oil and pulse until it starts to stick together. Test it with your fingers to make sure it's sticky enough. If it's too dry, add more water a tbsp at a time. Press crust evenly into mini tart tins and set aside in the fridge.
Add coconut milk and coconut sugar to a small saucepan and set over a medium heat. Bring to the boil for 7-10 minutes, until the mixture turns darker and slightly thicker. Reduce heat to a gentle simmer. Add in salt and tahini and stir well.
In a jug, mix plant milk with cornflour and vanilla. While the pan is still simmering, pour in the cornflour mix and stir well. After 2 minutes the mixture should start to thicken (it will thicken more as it cools). Allow to cool for 5 mins in the pan.Pour filling into tart shells and set aside in the fridge to set.
Prepare date caramel by blending dates, salt, nut butter and hot water together in a food processor. It should be thick, but pourable. Add more water if it's too thick.
Spread over a tbsp of date caramel on each tart and top with blueberries, mint and buckwheat.