Split the vanilla beans lengthwise and scrape out the seeds. Heat the milk and cream in a saucepan for 2 to 3 minutes, then add the vanilla seeds and pods. Remove from heat and let steep for 30 minutes.

Preheat the oven to 350°F (180°C). Once hot, place a water bath in the oven. Strain the vanilla mixture. In a mixing bowl, whisk the whole egg, egg yolks, and sugar, then add the vanilla mixture and whisk again.

Pour the mixture into ramekins and place them in the water bath in the oven. Bake for 20 to 25 minutes. The custard should be just set and slightly wobbly when done.