Prepare four glass containers with lids and set them on your counter. Mason jars or any wide-mouth jar with a lid work perfectly.
Make the milk base. In a large pitcher, whisk together the cold evaporated milk, cold whole milk, allulose, vanilla extract, and pinch of salt until the allulose is completely dissolved. This takes about one minute. Allulose dissolves cleanly in cold liquid.
Add the oats. Stir the high-protein oats into the milk mixture until combined.
Divide into jars. Pour the milk and oat mixture evenly into the four prepared containers, leaving room at the top for the orange juice you will add in the morning. Seal the containers.
Squeeze and chill the orange juice separately. Juice your oranges, pour the juice into a covered container, and refrigerate overnight. Keeping the juice separate until morning is what preserves the morir soñando technique and the fresh citrus flavor.
Refrigerate everything overnight, at least 8 hours, until the oats have absorbed the milk and the mixture has set into a thick, creamy base.
In the morning:
The magic pour. Open each jar and stir the oat base once. Then, while stirring slowly and steadily with a long spoon, pour the fresh orange juice over the oat mixture. Add a small squeeze of green lemon at the same time. Pouring slowly while stirring is the technique that creates the smooth, creamy emulsion and keeps the citrus from breaking the dairy. Do not rush this part.
Serve immediately while cold and frothy, or reseal and eat within the next 30 minutes. The orange juice is best added fresh each morning.