Chicken & veggie casserole Recipe

Chicken boneless cube 250gm
Potato small cube 2 &1/2 cup
Carrot small cube 1 cup
Green peas 1 cup
Butter 1tbsp +1tsp +2tbsp
Onion sliced 1/2 cup
Garlic cube 1tbsp
Black pepper powder 1/4 tsp +1/4 tsp
Flour 4tbsp
Full cream milk 1/2 litter
Grated mozzarella cheese 1cup
Parmesan cheese and paprika powder for topping ( optional)
1 beaten egg