Preheat oven to 400 degrees Fahrenheit. Spray a 2.5 quart casserole dish with cooking spray. In a food processor, blend together mushrooms, garlic, carrots and onion until smooth.
Break up ground turkey in a large saucepan over medium heat until no longer pink. Add in the pureed vegetables, stirring to combine. Mix in the ketchup, mustard, brown sugar, salt and pepper. Cook until warmed through. Stir in chickpeas. In a small mixing bowl, mix together baking mix, egg and milk until smooth.
Pour turkey mixture into an even layer on the bottom of prepared casserole dish. Pour baking mix over turkey and smooth out to create a flat top. Place in preheated oven and bake for 15-20 minutes, until top layer is cooked through and golden brown.
Cut into squares and scoop out onto plates. Serve and enjoy!
How to cook chickpeas: Place chickpeas in a large bowl and cover completely with cold water. Allow to soak overnight, about 12 hours. Once the chickpeas have soaked, drain them and transfer to a large cooking pot. Cover with water twice the amount of chickpeas and bring to a boil. Cover and allow to simmer for approximately one hour. Do a taste test to make sure they are tender enough for your liking. Drain and allow to cool for 15 minutes. Once chickpeas are cooled they are ready to be used. Cooked chickpeas can keep covered in the refrigerator for up to three days.