Make vegan pesto if you don't have any pre-made. Add all of the ingredients except for the olive oil to a food processor and blend. While it is running, slowly drizzle in the olive oil until combined.
Boil water and cook pasta according to package directions.
While the pasta is cooking, measure out 2 cups plant-based milk, 3 tsp tapioca starch, 1 tsp salt, 1 tbsp nutritional yeast and 1/4 cup vegan pesto into a medium-sized saucepan and whisk together.
Once combined, turn the heat to medium and cook, stirring frequently until it starts to boil.
Allow to boil slowly for 1 minute, then remove from heat.
Pour over drained and rinsed pasta, mix well, and serve hot.
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Notes
Make sure to mix the starch into the cold milk so it dissolves. (If you add starch to hot liquid, it will get lumpy.
Stir frequently while heating. The starch will settle to the bottom and become lumpy if you leave it.