Preheat the oven to 350f or 175c.
Place the cashews into a bowl and cover with boiling water. Leave to sit for 5 minutes.
Before making the sauce, remove all of the water from the defrosted frozen spinach. This can be done by pressing the spinach into a seive or by putting the spinach into a kitchen towel, gathering the edges of the towel and squeezing until all of the liquid is removed. Put the spinach into a bowl and set aside.
Heat a pan over medium heat on the stove and add the oil, onion, garlic and 1 tsp of salt. Sautee the onion + garlic until transluscent, roughly 5 minutes.
To make the cream sauce, drain the cashews and add them to a blender or food processor. Add the sauteed onions, garlic, chicken stock and the additional teaspoon of salt. Blend until smooth, scraping the sides as needed.
Take the bowl of drained spinach and using a fork, break apart the clumps of spinach. Add the cashew cream sauce and mix thoroughly.
Pour the spinach mixture into a 9x13 baking dish. Sprinkle the almond flour over the top if desired. Bake for 25-30 minutes or until golden brown + warmed through.