To make filling: Preheat the oven to 400°. Spray a 2-quart casserole with cooking spray. In a large sauce pan, heat olive oil and unsalted butter together. Add onion and sauté until tender, about 4 or 5 minutes. Add in flour until blended. Slowly stir in 2 cups of heated chicken stock, whisking well. Cook mixture over medium heat until thickened and bubbly, about 4 minutes. Stir in chicken, peas, potato, carrots, salt, pepper and Tabasco®. Pour into a 2-quart ovenproof casserole dish coated with cooking spray and spread mixture evenly.
To make crust: In a bowl, stir cornmeal, flour, baking powder, sugar and salt. Stir milk, egg and canola oil until well combined. Stir wet ingredients into dry ingredients. Spoon the batter evenly on the filling. Bake until the top is golden brown, about 22 to 25 minutes.