Preheat oven to 350°F, brush the salmon front and back with olive oil, and season liberally with smoked sea salt and freshly cracked black peppercorns. Place the salmon filet on a baking sheet lined with aluminum foil and bake for 30 minutes. 

Select the Saute function on the Instant Pot, add a tablespoon of olive oil; when the oil is hot, add the onions, celery, carrots, and garlic. Sauté until the onions become soft, use a slotted spoon, and remove the veggies into a bowl in about five minutes. 

Add the butter to the Instant Pot; when the butter has melted, whisk in the all-purpose flour, continue to whisk, and add the Old Bay seasoning. Little by little, add the chicken or vegetable stock until there are no lumps of flour. 

Pour in the coconut milk and cashew milk and continue to stir; when the mixture begins to steam, add the spinach, fold the cooked veggies back into the Instant Pot and add the shredded cheddar cheese and gently stir until the cheese is melted into the ingredients.

Cover the pot with the lid, do not lock the lid into place. Adjust the Instant Pot to the Warm setting. 

When the salmon is finished cooking, remove it from the oven and allow the salmon to rest for ten minutes. 

Divide the soup into serving bowls and flake three ounces of salmon into each bowl. Top with more shredded cheddar cheese if desired. 

Serve.