Turkey Pot Pie- more or less

I highly recommend cooking with the biscuits on top. The bottom will be moist but not soggy - especially if your filling is hot (crucial to not having under-done, soggy biscuits). I heat up the filling on the stovetop and when it's bubbling, quickly drop the biscuit dough in and cook in a hot oven. I'm sticking the link to my recipe in here - I don't normally toot my own horn, but this one is good and talks about exactly your situation. Good luck! https://food52.com/recipes/38434-poor-me-chicken-and-biscuits

Thanks for input. Dinner worked out great with biscuits baked on the casserole. Just the very bottoms where a bit squishy. I love Tetrazzini also and make that sometimes also. I think I love casseroles because my mother never made them.

If you haven't already made your dinner...
Some people do the biscuits on top of the stew and if their bottoms get soggy at all (sometimes happens), people like it.
But if you or some of your guests don't like the soggy texture, bake the biscuits separately, then everyone's happy.
Some can eat them straight from the oven, some can dunk them.

I make pot pie this way all the time and i bake the biscuits right on top of the filling. I never have a problem with them being soggy.

I went to a dinner last night and the host served Chicken Tetrazzini. It was absolutely delicious and haven't had it since the 80's. I bet your Turkey & biscuits could do well with this recipe.

My opinion, with the potpie, is to it all and place the biscuits towards the end of cooking to crisp and warm up a bit if they are made in advance.