In a large skillet over medium-high heat, cook bacon in a single layer until crispy. Transfer to a prepared plate with paper towels to drain and cool, leaving fat in skillet. Remove from heat. Crumble/chop bacon.

In a large pot over medium-high heat, combine the reserved shrimp shells, water, chicken broth, ½ cup white onion, garlic, cajun seasoning, cayenne, bay leaves, and 2 tbsp of the whites of the green onions. Stir and bring to a simmer. Adjust head to maintain a simmer and cook uncovered for about 40 min. Remove from heat and strain, discarding solids.

Return skillet with fat to medium-high heat. When fat is hot, add shrimp and cook until browned about 3 min, stirring constantly. Sprinkle with granulated onion. Transfer shrimp to a plate and set aside.

Set aside 2 tbsp of green parts of green onions. Add remaining green onions (white and green) and remaining 2 tbsp white onion to the skillet and cook, stirring often, until translucent 2-3 min. Add butter and stir until melted.

Turn the heat to medium. Add flour to the skillet and stir to combine. Add Kitchen Bouquet, stir constantly until the flour has browned but not burn. 15-20 min.

Add 3 ½ cups shrimp broth, about ½ cup at a time, stirring constantly to incorporate before adding more. When all broth is incorporated and mixture is a medium-thick gravy, turn the heat to low and simmer gently for 10 min. Taste seasoning and adjust with salt if needed. Turn heat to low and set aside.

Lightly coat the bottom and sides of a medium saucepan with nonstick cooking spray. Measure remaining shrimp broth and add water as needed to total 5 cups. Pour liquid into the prepared pan, set over high heat and bring to a boil. Gradually whisk in the grits stirring constantly, then add the salt. Return to a boil, the turn the heat to low, cover and cook 20 min until thick and smooth. Remove from heat and stir in butter.

Return gravy to medium heat. Once it's gently simmering, add bacon and shrimp. Turn heat olow and simmer until just cooked through, 5-10 min.

Ladle grits into bowls and top with shrimp and green onions.