Preheat oven to 180 degrees C (350 degrees F). Line a 17-18 cm (7 inch) cake pan with a circle of parchment paper. Grease well the pan on top.
In a medium bowl combine all purpose flour, coconut flour, baking powder and salt. Mix with a spoon to remove any crumbs.
In a large mixing bowl with an electric mixer beat together eggs and sugar until the mixture triples its volume. Add butter and vanilla and beat until absorbed. Add yogurt and whisk shortly, until combined.
Gradually add the dry ingredients, mixing gently with wooden spoon until absorbed.
Pour the batter into the prepared pan. Bake for 40-50 minutes or until a wooden skewer inserted in the centre comes out clean.
In a large mixing bowl combine mascarpone, sour cream and powdered sugar. Beat with an electric mixer until smooth.
Divide the mixture into two halves. Add the shredded coconut to one half. Mix well until combined.
Using a rubber spatula gradually fold the melted chocolate into the second half of the mixture. Mix gently until uniform.
Combine the white chocolate and the milk in a heatproof bowl. Place the bowl over a pan with gently simmering water (double boiler). Mix until the chocolate is melted and combined with the milk.
To assemble the cake:
Using a serrated knife cut the base into three equal layers. Trim any uneven parts and keep them aside.
Place one layer on a serving plate and frost it with half of the coconut frosting. Cover with another layer and frost with the rest of the coconut frosting. Place the third layer on top. Frost the cake all around with the chocolate frosting, leaving apart few tablespoons of it.
Break the trimmed parts of the cake base into crumbs and combine them with the leftover chocolate frosting. Mix well and make balls out of the mixture (if needed, refrigerate first). Coat some of the balls with coconut flour.
Spoon the glaze over the cake. Decorate with the truffles.