In a medium-sized jar or bowl, combine the ube halaya or ube extract, coconut milk, plant milk, and optional evaporated milk. Add chia seeds, sweetener, and vanilla extract if using. Whisk or stir for about 1-2 minutes until uniform.

Fold in the old-fashioned rolled oats until each oat is well coated. The oats should be fully submerged in the mixture.

Cover the jar securely and refrigerate overnight, or for at least 6 hours.

Before serving, stir the mixture to redistribute the oats. Add a splash of milk if too thick, and top with your favorite toppings.