Mix the oat, milk, chia seed, and date syrup in a jar. Close the lid and rest overnight in the refrigerator.
Next day, take the jar out of the refrigerator. Mix the yogurt and pistachio powder in a separate small bowl. Then transfer it to the jar. Do not mix them.
Pour the strawberry puree over the yogurt mixture. Sprinkle the chopped hazelnut and optionally strawberry slices on top of it.
You can take your dessert with you. When out of the refrigerator, it needs tobe consumed within 4 hours.