Preheat your oven to 350 degrees Fahrenheit.
Heat a large skillet over medium-high heat. Add ground beef and cook, breaking it apart, until no pink remains. Drain excess grease.
While beef cooks, combine biscuit mix and water in a bowl. Mix with hands until smooth dough forms.
Spray a 9x13-inch casserole dish with cooking spray. Press biscuit dough evenly into the bottom.
Bake the biscuit base for 5 to 8 minutes until set and lightly golden. Remove and set aside, keeping oven on.
Add chopped onion and bell pepper to the cooked beef. Cook for 4 minutes until softened.
Stir in taco seasoning and mix well. Remove from heat.
Spread the beef mixture evenly over the par-baked biscuit crust.
In a medium bowl, combine sour cream, mayonnaise, drained green chiles, three-quarters cup of cheese, and garlic powder. Mix until smooth.
Carefully spread the sour cream mixture over the beef layer.
Drop small spoonfuls of salsa across the top without spreading.
Sprinkle remaining cheese evenly over everything.
Bake uncovered for 30 minutes until hot, bubbly, and golden brown on top.
Let rest for 5 minutes before cutting and serving.
