- Preheat the oven to 300°F.
- Heat the cream, half-and-half and vanilla bean in a medium saucepan over medium heat just to a boil. Immediately turn off the heat. Set aside to infuse for 10 minutes.
- Whisk the egg yolks with the sugar in a large bowl just until combined. Whisking constantly, gradually pour in the hot cream mixture. Strain the mixture into the baking pan to smooth it and to remove the vanilla bean.
- Place the pan in the hot-water bath. Bake in the center of the oven until the custard is set but not too firm (it will cook a little more as it cools), 40 to 50 minutes. Remove from the water bath and let cool for 15 minutes.
- Tightly cover the custard with plastic wrap, making sure the plastic does not touch the surface. (The recipe can be made up to this point and kept refrigerated for up to 3 days.)
- Up to 4 hours before serving, fill the spoons with the chilled cooked custard by scooping each spoon into the pan of custard. Round the tops with a small spatula or a butter knife. Keep cold.
- Right before serving, thinly slice the banana (about 1/8-inch thick). Heat a broiler to very hot or fire up your kitchen torch. Top each spoonful of custard with a slice of banana, lightly pressing it onto the custard. Sprinkle the entire surface with a layer of sugar and place each spoon on a baking sheet. Broil or torch the spoons until the sugar is melted and well browned, about 1 minute. Let the spoonfuls cool for 1 minute before serving.