Heat a large Dutch oven over medium-high heat. When the pot is hot, add butter and let it melt completely.

Add the holy trinity blend to the Dutch oven. Stir and sauté until the veggies are tender and fragrant, approximately 5 minutes.

Add minced garlic to the Dutch oven and stir to incorporate. Sauté for 30 to 60 seconds until fragrant, then add 1 tablespoon Cajun seasoning and stir until well incorporated.

Pour in 2 cups chicken stock and 1 can diced tomatoes into the Dutch oven. Stir to incorporate and let the mixture come to a low boil. Once boiling, reduce heat to medium and simmer while preparing chicken.

Season all sides of the chicken with the remaining 1 tablespoon Cajun seasoning and set aside.

Heat a small skillet over medium heat. Once hot, add 1 tablespoon neutral oil and swirl to coat the pan. Continue heating until the oil is hot and shimmery.

Place chicken in the hot skillet. Cook for 3 to 5 minutes, then flip and cook for another 3 to 5 minutes until firm.

Transfer chicken to a cutting board and let it cool until comfortable to handle. Chop into bite-sized pieces and set aside.

Reduce heat under the Dutch oven to low. Let the mixture cool slightly, then add heavy cream and stir until fully combined.

Add chopped chicken to the Dutch oven. Stir to incorporate and let the ingredients simmer and meld for 3 to 5 minutes.

After simmering, taste the soup and adjust seasonings as needed. Portion into serving bowls and garnish with chopped green onions if desired. Serve warm.