In a medium-sized bowl or jar, mix together rolled oats, your preferred milk, and Greek yogurt until well blended. Add chopped shelled pistachios, chia seeds, honey or maple syrup, and vanilla extract. Stir until the mixture is cohesive and creamy.

Cover the bowl or jar tightly with a lid or plastic wrap, then place it in the refrigerator. Allow the oats to soak for at least 6 hours, or ideally overnight.

In the morning, stir the oats to combine ingredients well. If you prefer a thinner consistency, mix in a splash more milk. Top with additional chopped pistachios and fresh fruits or berries before enjoying.