Low Carb Shepherd’s Pie

4 -6 pieces bacon, chopped
2 lbs ground beef
1/2 cup onion, chopped
salt and pepper
1/4 teaspoon onion powder
1/4 teaspoon garlic powder
1 egg, beaten
8 ounces cheddar cheese, shredded and divided
16 ounces frozen green beans
16 ounces frozen cauliflower
3 tablespoons butter, divided
1/4 cup sour cream