While your skillet is baking, prepare the vanilla custard. In a small bowl, whisk 3 egg yolks and ¼ cup white sugar until pale and incorporated.
In a medium saucepan over low medium heat, heat the 1 ½ cups of heavy cream and vanilla until small bubbles form around the edge, right before simmering. Stir while heating to avoid curdling.
Temper the egg yolks by ladling out a small amount of hot milk and vigorously whisking it into the yolk/ sugar mixture very slowly.
Slowly add the yolk mixture to the hot milk pan, whisking vigorously to avoid the eggs cooking. Once combined, mix in a slurry of 1 tbsp corn starch and 1 tbsp water to help thicken over the heat. Once custard can coat the back of the spoon, it is completed. Remove from the heat and chill.
Once skillet has baked, allow to cool 10 minutes before serving and topping with vanilla custard.