In a small jar or container, add oats, milk, yoghurt, maple syrup, chia seeds, and protein powder (if using). Stir well so everything is evenly combined.
Pick one of the six flavours and stir the extra ingredients straight into the base mixture. For example, mash the banana for the peanut butter banana oats or grate the carrot finely for the carrot cake version.
Give it a good stir, making sure the oats are fully coated with liquid. Smooth the top down with a spoon.
Cover the jar with a lid and pop it into the fridge for at least 4 hours, but ideally overnight, so the oats can soak and soften.
In the morning, give your oats a stir. Add a splash more milk if you like them looser. Top with extra fruit, nuts, or a drizzle of nut butter for garnish, then enjoy straight from the jar.