Grind the pretzels in a food processor until fine crumbs. Combine with the butter and ¼ cup sugar and press into the prepared pie pan. Refrigerate while making the filling.
Puree 2 heaping cups of strawberries in a blender or food processor until smooth. Add to a saucepan with 1/3 cup sugar, cornstarch, lemon juice, and water. Cook, stirring constantly, over medium-high heat until the mixture comes to a boil. Let boil for 1-2 minutes or until thickened. Remove from the heat and stir in the Jell-O. Let the mixture cool for 30 minutes.
Cut the remaining strawberries in half and stir into the cooled Jell-O mixture. Spoon into the pie shell, arranging any berries as needed to make sure there are no holes. It looks prettiest if all the berries are turned cut-side down. Refrigerate for at least 4 hours. Can be made 2 days ahead.
Garnish with whipped cream and mint leaves, if desired.