1. Add egg yolks and sugar to a medium saucepan and whisk until a light yellow color and well-combined.
2. In another small saucepan, heat milk over medium-low heat until it just begins to simmer. Do not stir.
3. Gradually add milk to egg and sugar mixture, stirring constantly.
4. Return to heat until it reaches 165º or coats the back of a spoon. DO NOT let it come to a boil.
5. As soon as it reaches the correct temperature, remove from heat.
6. Pour custard base into an airtight container and store in the refrigerator until cool. The longer it chills, the creamier the ice cream will be.
7. Stir in the heavy cream and vanilla. Pour into ice cream maker and prepare according to the ice cream maker's instructions.
You can also add fillings as desired. If the filling easily falls apart, add when the ice cream is nearly finished.