In a large pot, heat a splash of water over medium heat, then add the chopped yellow onion. Sauté for about 5 minutes, stirring frequently, until the onion becomes translucent and fragrant.

Add a pinch of sea salt, red pepper flakes, diced celery, and chopped carrots. Stir everything together and cover the pot with a lid, allowing the vegetables to sweat for about 5-7 minutes.

Mix in minced garlic, diced golden potatoes, cashews, and vegetable stock. Bring the mixture to a gentle boil, then reduce the heat to low and simmer uncovered for about 20 minutes.

Carefully transfer the soup to a high-powered blender. Blend on high until the mixture reaches a silky smooth consistency, about 1-2 minutes.

Pour the blended soup back into the pot and stir in the broccoli florets. Cover the pot and simmer for an additional 3-5 minutes, or until the broccoli is just tender.

Taste the soup and adjust the seasoning with more sea salt if needed. Thin it out with a splash of vegetable stock if too thick.

Serve the creamy vegan broccoli potato soup hot, garnished with red pepper flakes and fresh chives.