Spray a 9x13 baking dish liberally with nonstick spray then set aside. Bring broth to a boil in a large saucepan then whisk in grits. Turn heat down to medium then cook for 5 minutes, whisking occasionally (a splatter screen is useful as grits will bubble and splatter). Remove from heat then add 1½ cups cheese, butter, salt and pepper and then stir until smooth. Pour into prepared baking dish then cover with plastic wrap and refrigerate until solid, at least 2 hours or up to overnight.
Preheat oven to 400°F. Run a knife around the outside edges of the baking dish then turn grits out onto a cutting board. Using a 2-inch round cookie cutter, cut out rounds then place on two parchment paper-lined baking sheets that have been sprayed with nonstick spray or use a sharp knife to cut grits into 2-inch squares (you will have less waste with this method). Bake rounds for 40 to 45 minutes or until golden brown, flipping half way through.
When rounds have 15 minutes left to bake, crisp bacon in a very large skillet over medium heat. Transfer bacon to a paper towel-lined plate to drain and remove all but 2 tablespoons bacon grease from skillet (add extra virgin olive oil if you need more fat). Turn heat up slightly then add shrimp, green onions and garlic then season lightly with salt and pepper and saute until shrimp are pink and cooked through, 3 to 4 minutes. Add cooked bacon in then stir to combine.
Top baked grit rounds with sautéed shrimp mixture then sprinkle with remaining ½ cup cheese. Turn oven to broil then broil until cheese is melted. Serve immediately.