Preheat the oven to 350 degrees Fahrenheit. Place 8 six ounce ramekins in a large roasting pan and set aside.
In a small heavy-bottomed saucepan over very low heat, combine ½ cup sugar with ¼ cup water. Bring to a boil and carefully watch it! Keep it on a soft boil until the sugar caramelizes and turns a light golden brown. This will seem like it's taking awhile, but happens faster than you think, so don't leave your stove. If you accidentally burn the caramel, you'll have to start over......and who's got time for that, right?
As soon as the caramel is a golden brown, remove from heat.
Carefully pour a small amount of caramel into each of the six ramekins, tilting the ramekins in a circular motion so that the caramel evenly coats the base of each. You'll use all the caramel in this step, so keep dividing it among the ramekins until the caramel is all gone. Let cool to room temperature while you make the custard.
In a small, heavy-bottomed saucepan over medium heat, combine the milk and the vanilla bean (or extract) and bring to a very low simmer. Now, before you start to worry about adding the hot liquid to your egg mixture (a couple of steps down), I've warmed the milk AND also added the milk and vanilla extract completely cold. I couldn't tell enough of a difference to be absolutely firm in needing to heat the milk. If this step gives you anxiety, skip to the next step (whisking the eggs) and add the milk/vanilla cold.
While you're waiting for the milk to heat up, in a large bowl (or the bowl of a stand mixer with the whisk attachment) whisk together the eggs, egg yolks, and remaining ½ cup sugar until fully incorporated. You want to whisk the mixture until it's frothy.
Whisking constantly, pour about a quarter of the hot milk mixture into the egg mixture. You're tempering the eggs and preventing them from turning into scrambled, so don't skip this step.
After you've tempered the eggs with some warm milk, slowly add the remaining hot milk mixture, constantly whisking while you add it.
Strain the custard mixture through a fine-mesh sieve into a large measuring bowl with pour spout.
Divide the custard mixture evenly between the caramel-coated ramekins.
Carefully pour boiling water into the baking dish so that it comes about ⅔ of the way up the sides of the ramekins. This is called a "bain-marie" which is a fancy term for a water bath. It creates a gentle heat and is often used to cook custards.
Carefully transfer the baking dish to the oven and bake until custard is just set, about 20-30 minutes. The custards are done when a butter knife inserted in the center of one of the ramekins comes out clean. My oven runs very hot, so my custards are usually done in 20 minutes. I highly recommend checking your custards early, so you don't over cook them.
Remove roasting pan from oven, and with an oven mitt carefully remove the ramekins. Refrigerate them until ready to serve, at least 1 hour.
When you're ready to serve, carefully run a knife along the edge of the ramekins and invert the ramekins onto a serving plate.
