Preheat the oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.
In a large skillet over medium-high heat, melt the butter, then cook and stir the onion, celery, carrots, and garlic until tender.
Stir in flour, sugar, salt, basil, and pepper.
Let it boil for 1 minute, then reduce the heat and stir in the peas.
Simmer for 5 minutes before adding the cooked chicken and stirring to combine.
Pour the chicken mixture into the prepared baking dish.
For the biscuits, mix baking mix and basil in a large bowl, then stir in milk to form a dough.
Divide the dough into 6 to 8 balls and flatten each one using your palm on floured wax paper to create rounds.
Arrange the biscuit rounds on top of the chicken mixture.
Bake for 30 minutes, then cover with foil and bake for an additional 10 minutes.
Serve by spooning the chicken mixture over the biscuits.