In a large pot, add all of the ingredients, stirring to combine and dissolve the miso and tomato paste.
Cook over low heat for 20 minutes. The goal is to have all the vegetables be tender but not reduce the liquid too much. Once the vegetables are tender, add to the blender and puree on high until smooth.
Remove from the blender into a sauce pot on medium and add the nutritional yeast and tapioca starch. It’s important to whisk the whole time as the tapioca starch hydrates and thickens the sauce. It tends to stick to the bottom of the pan. Cooking and whisking for 3 minutes, after that reduce the heat to low.
Cooking pasta Method
Place the water, plant milk, salt, and pasta in a medium-sized pot. Cooking over medium-high heat continually stirring the whole time. As the liquid reduces it is cooking the pasta, creating a starchy liquid that will add to the flavor and texture of the sauce. This takes about 5-7 minutes.
Add 1 ½ cups of the Mac and cheese sauce, and stir to combine. You can thin it with some plant milk if needed. Once the sauce and pasta are hot, it’s ready to eat.