Heat 2 tablespoons of the butter in a saucepan over medium heat until melted. Add the corn and scallion whites and saute for 5 minutes. Season with salt and pepper. Add 1 cup water. Using an immersion blender, blend the mixture until smooth. Add the stock and milk and bring to a simmer.
Slowly rain in the grits while whisking vigorously. Bring to a simmer and keep at a light simmer while stirring constantly, about 15 minutes. Add the cheese and remaining 2 tablespoons butter and whisk until smooth. If the grits are too tight, add a bit more water to loosen them up. Season to taste.
Meanwhile, heat the oil in a heavy-bottomed pot until a deep-frying thermometer registers 350 degrees F. Fry the shrimp until crispy, 3 to 5 minutes. Drain on a paper towel-lined plate.
Toss the hot crispy shrimp with the warm Cajun Butter. Spoon the shrimp over bowls of grits with some of the butter. Slice the reserved scallion greens very thinly on the bias and sprinkle on top.
Mix the paprika, sugar, cayenne, celery seed, garlic powder, onion powder, oregano, thyme, salt and pepper together in a bowl. Heat a 12-inch nonstick skillet over medium heat. Put the spice mixture in the skillet and toast to waken up the flavors, about 3 minutes. Add the butter and melt until foamy.