To make the lemon pie: Preheat the oven to 350ºF. Lightly spray a 9-inch plate with vegetable oil.
In a large bowl, combine the crushed graham crackers and 1/3 cup of the sugar and stir to blend. Stir in the melted butter until well blended. Press the cracker mixture onto the bottom and up the sides of the prepared pie plate. Bake until firm, about 8 minutes.
Meanwhile, in a stand mixer fitted with the paddle attachment (or in a large bowl with a handheld eclectic mixer), beat the condensed milk, egg yolks, and salt on medium speed for 4 minutes.
Pour the mixture in the baked pie crust. Return to the oven and bake until the center is set when the pan is gently nudged, about 10 minutes.
Cool the pie on a rack for 30 minutes. Place in the refrigerator until set, at least 1 hour and up to 3 days.
Just before serving, make the whipped cream topping: In a medium bowl, with handheld electric mixer, beat the cream, sugar, and vanilla on high speed until fluffy and the cream holds a soft peak when you pull the beater out of the bowl.
Spread the cream on the cooled pie. Garnish with fresh lemon slices, a sprinkle of lemon zest and mint sprigs.