1. Grease an 8 or 9 inch pie pan and preheat oven to 325°F (163°C).
2. Combine graham cracker crumbs, sugar and melted butter in a medium bowl and mix until combined.
3. Press the crumb mixture evenly into the bottom and up the sides of the pie pan, then bake for 8-10 minutes. Set aside to cool.
4. In a medium bowl combine the sweetened condensed milk, lemon juice and lemon zest then set aside.
5. In another large bowl, add the heavy whipping cream and powdered sugar. Whip on high speed until very stiff peaks form.
6. Add the mascarpone cheese to the whipped cream and whip on medium speed just until combined, then continue gently folding together until well combined.
7. Add about 1/3 of the lemon mixture to the whipped cream and gently fold to combine.
8. Add the remaining lemon mixture and gently fold to combine.
9. Add a little yellow icing color or food coloring, if desired.
10. Add the filling mixture to the cooled pie crust and refrigerate until firm, 4-5 hours.
11. To make the lemon whipped cream, add all four ingredients to a mixer bowl and whip until stiff peaks form.
12. Top the pie with some lemon slices and mint leaves and pipe swirls of whipped cream around the edge.
13. Refrigerate until ready to serve.