Yes, the creamy bacon sauce can be made the day before. Store it in an airtight container in the fridge. When you are ready to make the final dish place the pre-made sauce in a large frying pan and warm it gently. Stir through a few tablespoons of reserved pasta water to the sauce, and bring the sauce to a simmer. Reduce the heat, add the spaghetti and continue on with the recipe as instructed.