Juice limes and remove seeds. This pie is just not the same unless you use fresh key limes. This part takes time, but the result is worth it.
In a medium mixing bowl beat yolks together until frothy.
Add lime juice to yolks and blend until smooth.
Add sweetened condensed milk and continue to blend until smooth.
Pour filling into pie shell and bake at 350°F degrees for 25-30 minutes or until the top is lightly browned.
Allow pie to set on counter for 10 minutes then place pie in fridge til ready to serve. top with whipped topping.
I prefer to top with meringue. For a perfect key lime meringue use the 5 egg whites that were left over for the pie filling. Place in bowl and whip until peaks just start to form. Then add a scant amount of salt (about 1/4 tsp) and whip again for 30 seconds. Add in 9 tablespoons of sugar; adding 1 tablespoon at a time and whipping for about 30 seconds between each tablespoon. Last add 1/4 teaspoon lime juice and continue whipping until peaks are formed. Pile on top of pie and bake in 300 degree oven for about 10 minutes or until it is golden and the peaks are browned.