Cook macaroni noodles according to package instructions.
In a medium saucepan, melt the vegan butter over medium heat. Add the flour, mustard powder, garlic powder and sea salt. Whisk for about 1 minute until everything is combined.
Slowly pour in the non-dairy milk while whisking constantly. Simmer over medium heat, whisking often, until the sauce thickens (about 5 minutes).
Remove from heat and stir in the vegan cheese shreds until melted.
Add the cooked macaroni noodles to the saucepan and stir until all of the noodles are coated with sauce.