Preheat oven to 175C / 3560F and keep the oven rack adjusted to the middle position.
In a large bowl, mix the oats, almonds, hazelnuts, melted coconut oil, maple syrup and a pinch of sea salt together until well combined.
With the help of your hands, press evenly about 3 full tbsp of the mixture into 4 sprayed with oil 5-inch sized mini tart tins.
Bake in the oven for about 15 min, or until golden and crisp. Once ready, remove from the oven, and press the center of each tart with the back of a spoon to help reshape them (they may puff a bit in the oven).
In the meantime, prepare the mascarpone cream. In a large bowl, gently beat together the cheese and sugar until reaching a smooth and creamy consistency. Fold in orange zest and mix just until combined. Store in the fridge until needed.
Allow the tarts to cool completely before removing from their tins. Once cooled, use a sharp knife to carefully take them out. The crust is very delicate so be gentle during the process.
Fill each tart evenly with 2-3 tbsp of mascarpone cream. Top each tart with fresh blueberry, sprinkle with freeze-dried strawberry crumble and decorate with fresh mint leaves.
Serve immediately, or store in an airtight container in the fridge for up to 2 days.