Pot pie with a biscuit top

I threw together a pot pie for dinner yesterday.
I had about 1-1.5 cups mushroom gravy in the freezer that I warmed up in a sauce pan.
I diced up leftovers of two half onions (one yellow, one red), three cloves of garlic, 2 carrots, one stalk of celery, two potatoes, and about 5 or 6 baby portabella mushrooms. I saute'd those all in olive oil until soft.
Then I whipped up a recipe of baking powder biscuits from the Betty Crocker cookbook and put that on top. I had a little extra which I cooked on a sheet with dinner.
I put everything in a casserole dish (gravy and cooked veggies together and biscuit on top) and baked it for about 20-25 min at 450degF.
I thought it turned out pretty good, but it was a little under seasoned - could have used some salt and pepper. Green beans or peas would also have been a good addition.