Preheat the oven to 325 degrees F. Place the eggs in a bowl. Whisk in the condensed milk. Whisk in the lime juice. Pour the mixture into the pie crust; bake 20 minutes. Cool the pie on a baking rack until room temperature, and then chill well in the fridge. Whip the cream until soft peaks form. Whip in the icing sugar and continue beating until stiff peaks form. Cut the pie into wedges. Top wedges of the pie with a dollop of whipped cream. Garnish with key lime slices, if desired.
Note: Graham cracker pie crusts are available in the aisle baking supplies is sold. You could, of course, make your own.