Chocolate Ganache Tartlets

Ingredients

• 1 1/2 sticks (6 ounces) unsalted butter, chilled and cut into small pieces
• 1/2 cup confectioners' sugar
• 1/4 teaspoon salt
• 1 egg, lightly beaten
• 1 tablespoon ice-cold water
• 1 cup heavy cream
• 1/2 cup granulated sugar
• 2 ounces high-quality dark chocolate (at least 70% cocoa), finely chopped
• 1 teaspoon vanilla extract