Set the oven to 350F. Cook sausage most of the way and melt the butter.
Blend the chopped vegetables and butter in the blender. Slowly add cooked sausage and blend as well.
Put half of the dry stuffing mix into a large pot and pour some of the sausage/vegetable mixture over the stuffing mix. Add 1/2 cup of water to the blender with the rest of the sausage mixture, then pour this into the rest of the dry stuffing mix and the other portion in the pot.
Add seasonings and the rest of the hot water to the pot and stir until combined and not crunchy when tasted.
Pour well-combined stuffing mixture into a casserole dish. Cover with foil and bake for 45 minutes. To reheat, bake at 350F for 20 minutes covered and 10 minutes uncovered.