Melt the butter over medium heat in a large skillet and add the cauliflower, onions, garlic and sea salt. Sauté for about 10 minutes until the cauliflower is softened. Pour the cauliflower mixture into a food processor and add the cream. Pulse for ten 1-second pulses, until the mixture is the consistency of grits.
Wipe out the skillet that was used for the grits, and melt 2 tablespoons of butter over medium heat. Add the onions and mushrooms and cook for 10 minutes, until softened and just turning golden brown on the edges. Add the spinach and cook until wilted, about 3-4 minutes. Add the broth and cream and simmer until the sauce reduces by half and begins to thicken.
Toss the shrimp, herbamare, paprika, cayenne and garlic powder in a small bowl. Add the seasoned shrimp to the mushroom sauce. Cook for 5-7 minutes until shrimp is cooked through, stirring occasionally.
To serve, spoon some of the grits into a bowl and top with the shrimp and mushroom sauce.