Preheat the oven to 400°F.
Roast the turkey breast lightly in the oven with a sprinkle of fresh herbs until just cooked through, then chop into small bite-sized pieces.
In a medium saucepan over medium heat, melt the light butter. Add chopped carrots, celery, and mushrooms, and sauté until they begin to soften, about 3-4 minutes.
Stir in the whole wheat flour and cook for an additional minute to form a light roux.
Gradually whisk in the low sodium chicken broth and low-fat milk, stirring continuously until a smooth, slightly thickened sauce forms.
Add the turkey pieces, green peas, and fresh herbs to the sauce, and simmer for 2-3 minutes to meld the flavors. Adjust seasoning with salt and pepper as desired.
Place the turkey and vegetable mixture into an oven-safe ramekin or small baking dish. Top with the phyllo dough sheet, gently pressing the edges to seal the filling.
Bake in the preheated oven for 10-12 minutes, or until the phyllo is crisp and golden.
Let cool slightly before serving, and enjoy your nutritious, creamy herb-roasted turkey pot pie.