In a medium-sized jar or bowl, combine the rolled oats, your choice of milk, Greek yogurt, chopped pistachios, chia seeds, honey or maple syrup, and vanilla extract. Stir vigorously until the mixture is well incorporated.

Cover the jar or bowl with a lid or plastic wrap, and place it in the refrigerator for at least 6 hours or overnight.

When you're ready to enjoy, remove from refrigerator, stir, and add a splash of milk for a thinner consistency if desired. Top with additional chopped pistachios and fresh fruits.