Pour the milk and heavy cream into a saucepan. Add the split vanilla bean. Bring to a boil, then remove from heat and let steep for 30 to 40 minutes.

Strain the mixture through a fine mesh sieve. In a mixing bowl, combine the egg yolks and sugar with a wooden spoon. Gradually add the strained vanilla milk, stirring well with the spoon.

Divide the mixture among 4 ramekins. Place the ramekins in a baking dish filled with water (water bath). Bake for 30 to 40 minutes in the oven at 320°F (160°C). Check for doneness by gently shaking the ramekins; the custard should jiggle like a flan.

Let cool to room temperature, then refrigerate for 4 hours. Before serving, sprinkle the tops with light brown sugar. Caramelize the sugar lightly under the oven broiler or with a kitchen torch.