1. Place the chopped carrots and potatoes into a large pot and fill with water, bring the water to a boil. Once boiling, lower the heat to a simmer, let the vegetables cook until very tender, about 10 minutes. 

2. While the vegetables are steaming, add the water, nutritional yeast, starch (if using), lemon juice, salt, smoked paprika (if using) to your blender pitcher. 

3. When the steamed vegetables are tender, lift them out of the pot and add them to the blender, LET THIS COOL BEFORE BLENDING. Blend until the mixture is very smooth-- it will be runny. 

4. Drain the sauce pot of the water from the steaming process, then pour the blended mixture into the empty pot. Heat the sauce over medium heat, stirring with a whisk until it thickens, about 3 to 5 minutes. Slowly whisk in the non-dairy milk until you reach your desired consistency. 

5. Add more salt to taste, then serve right away. This sauce is best used immediately, but it can be cooled completely and stored in an airtight container for up to 2 days in the fridge. Gently reheat the sauce when ready to use, but do not bring it to a boil.