Vanilla Sandwich Cookies with Chocolate Filling
For the dough: In a bowl, mix together the flour, sugar and vanilla sugar. Make a well in the center, add the egg and the butter.
With a pastry blender or two knives, cut in the butter until the mixture resembles coarse crumbs.
Quickly knead with your hands until the dough just comes together. Flatten to a disk, wrap in plastic wrap and refrigerate, 30 minutes.
On a floured surface, roll the dough out 3 to 4 mm (approximately 1/8-inch) thin.
Loosen the dough with a spatula so it doesn't stick to the board.
Preheat the oven to 180°C (approximately 350°F). Line a baking sheet with parchment paper.
Using a round cookie cutter with a serrated edge cut out about 40 cookies, place 1-inch apart on the baking sheet, and bake until set, 10-12 minutes.
With a spatula, transfer the hot cookies ot a wire rack to cool completely.
For filling and decorating: Coarsely chop the chocolate and melt with the cream in a heatproof bowl set over a pan of simmering water. Cool slightly, spread over half the cookies and top with the remaining cookies.
In a bowl, mix the powdered sugar with 1 - 2 tablespoons of water until it's spreadable. Color with food coloring and spread over the cookies. Immediately sprinkle with coarse sugar and let dry.