1. Split vanilla pod in half, and scrape out the seeds using a knife. Pour milk into a saucepan and add the pod and seeds. Bring to a boil over medium heat.
2. Place egg yolks in a mixing bowl with sugar and whisk until the mixture becomes pale and frothy.
3. When the milk starts boiling, pour about one-fifth of the milk onto the egg yolks and sugar mixture while whisking vigorously off the heat.
Lastly, pour the custard back into the saucepan and cook on low heat while stirring constantly with a spatula. The custard is cooked when it coats the back of the spatula. To check, run a finger over the spatula, the trace should remain clear. Pour the custard into another container and let it cool at room temperature, stirring regularly to avoid lumps.