Easy Key Lime Pie Recipe

1 (9 or 10 inch) prepared graham cracker crust
6 egg yolks
2 (14 oz.) cans sweetened condensed milk
1 (8 oz.) bottle lime juice or juice of 3 limes (or key limes, if available)
Whipped cream or Cool Whip

Preheat oven to 325 degrees. In large mixer bowl, beat yolks with milk and lime juice. Pour into prepared pastry shell; bake 40 minutes, cool. Chill. Top with whipped topping to serve. Keep refrigerated.