Cook onion and celery over a medium to high heat until past softened stage, then add mushrooms, stirring until cooked through.
Mix in bread crumbs until well incorporated.
Remove from heat and add sage, parsley, salt & pepper, then mix in the beaten eggs – stir vigorously or the eggs will cook too quickly and be difficult to blend in.
This should comfortably fit into a loaf pan, bake in the oven for about an hour, alongside your turkey or chicken. The top will be crispy. This stuffing is especially delicious with gravy.