Cook pasta according to package instructions. If you want a really saucy Mac, use 12 oz of pasta. For a more balanced Mac, use 1 lb.
While the water is heating up and the pasta is cooking, prepare the cheese sauce by melting vegan butter in a large saucepan.
Once melted, add the garlic powder, onion powder, smoked paprika, and mustard powder, whisk and cook for 1 minute. I recommend starting with 1/4 tsp of some of the seasonings and adding more later. A little goes a long way and you can always add more, you can't subtract!
Then whisk in the flour 1 Tbsp at a time. After all the flour has been whisked in, cook for 1 - 2 minutes.
Next whisk in the plant milk about 1/2 cup at a time. Start with 2 cups of milk at first. Bring to a light boil.
Add in the vegan cheese and stir until melted. Add more plant milk if it's too thick. Taste and adjust for seasoning adding any salt, spices, hot sauce, whatever you like!
Add in the cooked pasta. Reserve some of the pasta water in case it's needed.
Stir the pasta in and taste for seasoning. Add in some pasta water if the sauce is too thick. Likewise, if it's too thin, add in 1 Tbsp of Tapioca Starch. Keep in mind, the sauce will tighten as it cools too.
Store leftovers in the fridge for up to 3 days. Heat on the stovetop or microwave. You may need to add some plant milk / water if it's a bit dry.