Initiate Cooking: In a sizable pot, heat a tablespoon of olive oil over a medium-high flame. Introduce the onion and garlic, sautéing for two minutes until they become semi-transparent, ensuring they do not brown.
Add Vegetables: Toss in the diced carrots, celery, and finely chopped capsicum, stirring them into the mixture for a brief minute to slightly soften.
Incorporate Butter and Flour: Fold in the butter until completely melted, followed by a gradual sprinkling of flour. Stir this mixture vigorously for a minute to form a smooth base.
Combine Liquids and Seasonings: Slowly pour in the chicken broth, stirring meticulously until the flour blends in seamlessly, then proceed to mix in the milk. Stir the concoction well before adding the designated salt and an assortment of spices - garlic powder, onion powder, dried thyme, and black pepper along with the diced or shredded cooked chicken and peas.
Let it Simmer: Transition the heat to a point where the soup can simmer gently, stirring from time to time to prevent any sticking to the bottom. The mixture should start to thicken within 4 to 5 minutes; monitor closely to avoid boiling.
Final Adjustments: Post-thickening, taste and tweak the salt and pepper as needed. Serve this aromatic delight in bowls, perhaps adorned with croutons and a hint of fresh thyme for an elevated touch.
Crouton Preparation: For the croutons, lightly coat cubed white bread with olive oil spray and a pinch of salt. Spread these on a baking tray and toast in the oven at 180°C (350°F) until they achieve a golden, crunchy exterior, which should take around 5 minutes.