Place a 12-inch sauté pan over medium-high heat, and add the bacon. Sauté until golden brown. Remove bacon and reserve. Remove all but a tablespoon or two of the drippings and set the excess aside.
Sprinkle the shrimp with a healthy tablespoon of the spice blend. Sauté in the oil until just done, two to three minutes. Remove and set aside.
If necessary, add a little of the reserved drippings to the pan. Add the onion and peppers, cooking until nearly soft. Add the garlic and the white portions of the green onion, and saute for a moment more. Add the remaining Cajun Spice to the pan, stirring briefly, then add the stock and bring to a boil. Reduce to a simmer and cook until the stock has reduced by about half.
Return the bacon and shrimp to the pan, heat through. Remove from heat and garnish with the green portions of the green onion and the parsley. Serve over grits, drizzle the Cajun gastrique around the dish. Garnish with lemon.
Notes: for a more traditional Shrimp and Grits, 1/2 cup of cream can be added after the reduction.