Preheat your broiler on high and position the oven rack in the upper third of the oven.
In a blender, combine the egg whites, whole egg, low-fat cottage cheese, whole milk, vanilla bean paste, and erythritol. Blend until the mixture is completely smooth and uniform.
Pour the blended custard mixture into a small, oven-safe ramekin or custard dish.
Place the ramekin in a baking dish and add hot water until it comes halfway up the side of the custard dish, creating a water bath.
Bake in the preheated oven for about 25-30 minutes, or until the custard is just set around the edges but still has a slight wobble in the center.
Remove the ramekin from the water bath and let it cool slightly.
Sprinkle the light brown sugar evenly on top of the custard.
Using the broiler, caramelize the sugar by broiling for 1-2 minutes until the top is golden and bubbly. Keep a close eye to avoid burning.
Allow the custard to cool for a few minutes before serving to let the caramelized top harden slightly.