Toss shrimp with Cajun seasoning, cover with plastic wrap and refrigerate.
Heat oil in a large heavy-duty Dutch oven over medium heat. Add sausage and cook for 6-8 minutes or until sausage is nicely browned. Remove with a slotted spoon and set aside.
Add flour to oil and cook over medium-low heat, stirring frequently, until mixture turns a deep golden brown color, slightly darker than the color of peanut butter. This will take about 10 minutes. If the mixture is darkening too quickly, reduce heat.
Add onions, peppers and garlic. Cook, stirring occasionally for 8-10 minutes until onions begin to soften.
Add the chicken stock, carrots, spices and pepper. Stir well. Bring to a boil, then reduce to a slow simmer. Cook for 25-30 minutes, uncovered until carrots are very tender.
Add shrimp and reserved andouille sausage, stir to combine, then return gumbo to a boil. Cover pot and turn off the heat. Let gumbo sit, covered for 10 minutes before serving. The shrimp will cook perfectly during this 10 minute resting time. Taste and season, if needed. Serve in bowls with basmati rice. Garnish with sliced green (spring) onions.
Notes
See Café Tips for more detailed instructions and tips.