To make the pastry, whisk together flour, sugar and salt in a large bowl. Using a pastry blender or your clean fingers, cut or rub butter into flour until it resembles coarse bread crumbs. The butter should be well dispersed with only very small pieces remaining. Whisk egg yolk with water in a small bowl and drizzle into flour mixture while gently stirring with a fork. Continue to stir until dry ingredients are moistened and it holds together in clumps. Turn dough out onto a clean work surface and it bring together in a ball with your hands, turning it frequently and pressing in loose bits until it is cohesive. Shape dough into a disk, wrap well with plastic wrap and refrigerate until firm, at least 1 hour.

Place dough on lightly floured work surface and roll it out to ⅛ -inch thickness, using more flour as needed to prevent sticking. Use a 2.5-inch round to cut out circles. Gently fit the dough rounds into the base of a miniature 24-cup muffin tin, gently pressing the dough into the bottom and allowing the edges to fold and crimp. Refrigerate until firm, about 15 minutes. Position a rack in the center of the oven and preheat the oven to 350°F.

Prick the bottom of chilled tart shells with a fork and bake until golden, about 8 minutes. Transfer to a wire rack to cool completely.

To make the filling, place chopped chocolate in a medium bowl. Bring cream to a boil in a small saucepot over medium-low heat and pour immediately over chopped chocolate. Let stand 5 minutes. Stir gently with a rubber spatula, starting in the center and working your way out to the edges until completely melted, smooth and glossy. Stir in brandy. Let mixture cool at room temperature until it reaches spreading consistency, about 1 hour, stirring every 10 minutes. Pour ganache into a pastry bag fitted with a star tip and pipe it into cooled tart shells. Decorate as you wish.