Blend roasted buckwheat, oat flakes, and Himalayan pink salt in a food processor until finely ground. Mix in solid coconut oil, maple syrup, and cashew butter until it forms a dough-like consistency. Press into the base and up the sides of a tart tin and freeze for 30 minutes.

In a blender, combine the mango chunks, passion fruit juice, chilled coconut milk, vanilla extract, and maple syrup. Blend until smooth and creamy.

In a small glass, dissolve agar agar powder in mandarin juice. Heat in a saucepan over low heat until it thickens, stirring constantly for about 2-3 minutes.

Gently heat the blended mango filling in a saucepan over low heat until it begins to simmer. Whisk in the activated agar agar mixture until fully incorporated. Continue to whisk for about 2-3 minutes until filling thickens slightly.

Carefully pour the creamy filling over the prepared crust. Allow to cool at room temperature for 10 minutes, then refrigerate for at least 1 hour or until set.

Remove the tart from the fridge. Gently release from the tin and slice into wedges. Garnish with fresh passion fruit pulp and a sprig of mint. Serve immediately.