Start by washing and peeling your potatoes, sweet potatoes, carrots, and onion. Dice them into small, uniform pieces to ensure even cooking. Mince the garlic clove.
In a medium pot, add the diced potato, sweet potato, carrot, onion, and minced garlic. Pour in 3 cups of veggie broth. Bring to a boil over medium-high heat, then reduce to a simmer. Cook for about 15-20 minutes or until the veggies are tender.
Once the veggies are cooked, reserve 1 cup of the cooking water and drain the rest. Transfer the cooked veggies to a high-speed blender or food processor. Add the reserved cooking water, sunflower seeds, nutritional yeast, corn starch, lemon juice, hot chili powder, smoked paprika, salt, pepper, and Sriracha (if using).
Blend on high until the mixture is completely smooth and creamy. You may need to scrape down the sides a couple of times to ensure everything is well incorporated. If the sauce is too thick, add a little more veggie broth until you reach your desired consistency.
Taste the sauce and adjust the seasoning as needed. If you prefer a spicier kick, add more Sriracha or chili flakes. Serve immediately over nachos, tacos, or as a dip, and enjoy!