Preheat your oven to 400°F.
Dice the chicken breast into small pieces and season with a pinch of salt and pepper.
Chop the carrot, celery, and onion into uniform bite-sized pieces.
In a medium saucepan, heat the olive oil over medium heat. Sauté the onions until softened, about 2 minutes.
Add the diced carrots and celery, stirring for another 3-4 minutes until they begin to soften.
Sprinkle the whole wheat flour over the vegetables and stir to combine, cooking for about 1 minute to eliminate any raw flour taste.
Gradually whisk in the low-fat milk and chicken broth until a smooth sauce forms. Add in the peas and bring the mixture to a simmer.
Stir in the diced chicken and let the filling simmer for 5-7 minutes until the chicken is fully cooked and the sauce thickens slightly.
Transfer the filling into a small, oven-safe pot or ramekin. Optional: Top with a light whole grain biscuit or a sprinkle of whole wheat crumbs if desired, though this version skips a crust for a cleaner meal.
Bake in the preheated oven for 12-15 minutes to meld the flavors and heat through.
Remove from the oven, let it cool slightly, and serve warm.