Preheat the oven to 400ºF.
To make the crust, in a bowl, combine the olive oil, butter, water, lemon juice, if using, aniseeds, flour, granulated sugar, and salt and stir with a wooden spoon until the ingredients combine together in a rough dough. Turn out the dough onto a lightly floured work surface and knead for about 10 minutes, or until soft and no longer sticky.
Clean the work surface, dust again with flour, and roll out the dough into a thin round at least 13 inches in diameter. Carefully transfer the dough round to a 10-inch springform pan with 2-inch sides, pressing it into the bottom and sides. Trim away the excess dough even with the pan rim.
To make the filling, combine the mint leaves, lemon zest, and granulated sugar in a blender or food processor and process on high speed until you have a mixture of fine particles.
Add the cheese, eggs, and lemon juice and process until smooth.
Pour the mixture into the crust.
Bake the tart for 30 minutes, or until set when tested with a knife in the center. Transfer to a wire rack and let cool in the pan. Remove the pan sides and slide the tart onto a flat serving plate. Garnish with the mint leaves and dust white confectioners' sugar. Serve at room temperature.