Preheat your oven to 350°F (175°C). In a food processor, combine oats and ground almonds until finely blended. Mix in salt, melted vegan butter, and maple syrup until fully incorporated. Press this mixture firmly into a tart pan, creating an even layer. Bake for 15 minutes, or until golden brown and fragrant, then allow it to cool completely on a wire rack.

In a saucepan, bring raspberries and half a cup of water to a boil over medium heat. Let it simmer for about 3 minutes until the berries become soft and you can mash them easily. Dissolve agar powder in the remaining water, then combine it with the mashed raspberries and sugar. Cook for another 2 minutes until slightly thickened, then remove from heat and allow to cool briefly before pouring it into the cooled crust.

Set up a double boiler or a heatproof bowl over a pot of simmering water and melt the vegan white chocolate. Once melted, stir in warmed coconut cream until the mixture is smooth and creamy. Pour this luscious white chocolate mixture over the chilled raspberry layer in the tart, spreading it evenly with a spatula for a smooth finish.

Cover the tart with plastic wrap and place it in the refrigerator. Allow it to chill for at least 3 hours, or overnight if possible, until the layers have fully set.

Before serving, carefully remove the tart from the pan and garnish it with fresh raspberries, sugared cranberries, or desiccated coconut as desired. Slice into wedges with a sharp knife, and serve chilled.