You can prepare this dish for baking in advance and cook for 30-40 minutes in the oven. However, sometimes cooking the sauce this way with the vegetables can cause the sauce to split and become runny. I prefer to prepare the sauce and vegetables and keep separate in the fridge. Cover the casserole dish with foil and place in the oven and in the meantime reheat the sauce until smooth. Remove the foil and drain any liquid then pour over the sauce and heat until piping hot. Although you can reheat this dish if you have prepared and cooked it the same day, the sauce texture is not as good.