Prepare a 13x9 pan with nonstick cooking spray and set aside.
Add the milk, chicken stock, onion, and garlic to a small Dutch oven and heat over medium high heat until simmering vigorously, but not a rolling boil.
Remove from the heat and stream in the grits while whisking.
Place the grits back on the stove and cook on low. Add salt and pepper and cover with a lid. Stir frequently, focusing especially on the bottom and sides of the pan, where grits are most likely to stick and burn. Cook until the grits are thickened, but still pourable, about 15 minutes.
Remove from the heat and stir in the butter until completely incorporated. Pour into the prepared pan and let cool to room temperature, about 30 minutes. Cover in plastic wrap placed directly on top of the grits. Place in the refrigerator for at least 2 hours until firm.
Once you are ready to cook, stir the flour and seasoned salt together and place in a pie plate or other shallow dish. Then use a 2.5-inch round cutter to cut out circles of chilled grits. Coat both sides of the rounds in seasoned flour and shake off any excess.
Heat one inch of oil in a large nonstick or cast iron skillet over medium heat until hot. When the oil reaches about 350°F, gently lower half of the floured grit cakes into the oil and cook for 2-3 minutes until golden brown on the bottom. Gently flip the cakes on the other side and continue cooking for another 2 minutes. Remove the cakes and drain on a paper towel-lined plate. Allow the oil to return to temperature and repeat with the remaining cakes. Enjoy hot!