In a large mixing bowl, combine flour, salt, and a pinch of cinnamon, and mix well. Cut in chilled butter using a pastry cutter until the mixture resembles coarse crumbs. Add sugar and egg yolks, mixing until just combined. Shape the dough into a disc, wrap in plastic, and refrigerate for at least 1 hour.

Preheat your oven to 190°C (374°F). Roll out the chilled dough on a lightly floured surface to about 1/4 inch thick. Gently press the dough into tartlet tins, ensuring to cover the sides. Line with parchment paper and fill with baking weights, then bake for 10 minutes. Remove weights and bake for an additional 5 minutes until golden brown. Let the tart shells cool completely on a wire rack.

In a medium mixing bowl, beat the egg yolks and sugar until pale and creamy. In a saucepan, heat the heavy cream over low heat until warm but not boiling. Gradually whisk the warm cream into the egg mixture, then return everything to the saucepan. Cook gently over low heat, stirring constantly until the mixture thickens slightly and coats the back of a spoon. Stir in the melted white chocolate until smooth, then let it cool completely.

In a separate mixing bowl, whip the remaining heavy cream to medium-stiff peaks. Be careful not to overwhip. Once the chocolate mixture has cooled, gently fold in the whipped cream until fully incorporated.

Carefully fill the cooled tart shells with the mousse filling, smoothing the tops with a spatula. Cover the tarts with plastic wrap and refrigerate for at least 4 hours or preferably overnight.

Before serving, consider adding a touch of elegance by garnishing with fresh berries or drizzling with dark chocolate sauce.