Freeze the banana (best if done the night before) (store-bought frozen fruit will work as well): Slice the banana and transfer it to a small baking sheet or plate lined with parchment paper. Transfer the sheet or plate to the freezer and allow it to freeze completely.
Add the milk and yogurt to a blender, along with the frozen banana and acai. Blend until smooth, adding additional milk if needed.
Brew the coffee.
Prep the frappuccino: In a bowl whisk the heavy cream until stiff peaks form.
For the frappuccino: Pour milk into a saucepan and place over medium heat. Add in the caramel sauce and whisk continuously until it is frothy.
Divide the smoothie into bowls and top with granola, blackberries, raspberries, coconut flakes, and hazelnuts.
Pour the coffee into a mug, then pour in the frothed milk, top with whipped cream, and drizzle with caramel. Add sugar if needed to taste.
Serve the acai bowl with Frappuccino topped with a pinch of flaky salt.