Add egg yolks and sugar to a medium saucepan and whisk until a light yellow color and well combined. In another small sauce pan, heat milk over medium-low heat until it just begins to simmer. Do not stir. Gradually add milk to egg and sugar mixture, stirring constantly. Return to heat until it reaches 165 ºF, but do not allow it to come to a boil. As soon as it reaches the correct temperature, remove it from the heat. Pour custard base into an airtight container and store in the refrigerator until it chills to 65 ºF. The longer the custard base chills, the creamier your ice cream will be.
Once the custard base is ready, stir in the heavy cream and vanilla extract and pour it into your ice cream maker and process according to your ice cream maker’s instructions.