Kelp seaweed is commonly used in Chinese, Japanese, and Korean cuisines, and as a vegetarian I have been using it to add depth to Asian dishes where I omit fish- or shrimp-derived ingredients. I bet it would be great in this vegan chickpea of the sea tuna sandwich, as well. Although the flavor evokes the ocean, it is not overwhelming, and many people simply use kelp powder as a salt substitute.
I found this kelp powder in the salt aisle at a Korean grocery store. Kelp powder is also available from some herb merchants and health food shops, as it's a good source of vitamins, minerals and trace elements, including iodine, calcium, and iron. One could also make a DIY version by grinding dried kombu sheets.
Have you ever cooked with kelp powder?
Related: Umami for Vegans
(Image: Emily Ho)