Select Sauté on the Instant Pot and add the oil.
Once hot, add onions and salt and cook until onions are softened.
Stir in ginger, coriander, fennel, and cinnamon and cook until fragrant, then add the stock water, carrots, and baking soda, and use a wooden spoon to deglaze the base of the inner pot. Then press cancel.
Secure the lid and select Pressure Cook and set the time for 3 minutes.
When the cooking program has finished, quick release the pressure then remove the lid.
Working in batches, process soup in blender until smooth, and then return the processed soup to Instant Pot.
Select Sauté again and bring the soup to a simmer. Season with salt and pepper to taste.
Drizzle individual portions with pomegranate molasses and top with yogurt, hazelnuts, and coriander before serving.