Vigorously whisk the plant milk, chia seeds, maple syrup, and vanilla together in an airtight jar or container until the chia seeds are distributed throughout the liquid. Refrigerate for at least 8 hours or overnight to thicken.

In the morning, vigorously whisk the chia pudding. If it's too thin, add in more chia seeds, 1 tablespoon at a time, to thicken. If it's too thick, add in more plant milk, 1 tablespoon at a time, to thin.

Make the soft serve just before serving. Add the frozen strawberries, blueberries, and dates (if using) to a food processor and process until smooth with a sorbet-like texture, stopping to scrape down sides as needed. You might need to add in a very small amount of plant milk to get it moving. I recommend adding 1 tablespoon at a time and adding as little as possible to maintain a thick, soft-serve texture.

In two jars or parfait glasses, layer the chia pudding and berry soft serve, one after the other. Sprinkle with desired toppings and serve immediately.