Start by dicing the chicken into bite-sized pieces if it's not already done. Chop the onion, mince the garlic, and prepare the tomatoes.
In a large pot or Dutch oven, heat a tablespoon of olive oil or melt butter over medium heat. Add the chopped onion and minced garlic. Sauté until they become translucent and aromatic.
Add the diced chicken to the pot with the sautéed onions and garlic. Cook until the chicken is no longer pink and starts to brown slightly.
Pour in the diced or crushed tomatoes into the pot. Stir well to combine them with the chicken and aromatics.
Season the mixture with herbs like basil, oregano, and thyme. Add salt and pepper to taste. Pour in the chicken broth or stock.
If you prefer a smoother texture, you can use an immersion blender or transfer portions of the soup to a blender to puree until smooth.
Once the soup has simmered and reached the desired consistency, reduce the heat to low and pour in the heavy cream or half-and-half.
Taste the soup and adjust the seasoning if needed. Ladle the thick and creamy chicken tomato soup into bowls and garnish with fresh herbs if desired. Serve hot with crusty bread or crackers.