Preheat oven to 350 degrees. Lightly grease a 9x13x2-inch pan.
Add your vanilla wafers to a food processor and chop to a fine consistency.
Make the crust by combining the flour, vanilla wafers, confectioners sugar, and salt in a large bowl. Cut in the butter to make a crumbly mixture. Press the mixture into the prepared pan. (You may need to dip your fingers into a little flour or confectioners sugar to keep the dough from sticking to your fingers.) Bake for 20 minutes.
Meanwhile, to make the filling, mix the eggs, granulated sugar, flour, True Lemon and water. Pour this over the baked crust and bake for 25 minutes longer.
In a food processor blend your confectioners sugar and mint together, until its evenly combined. Sprinkle with the mint-sugar, if desired, when the bars are done.