To make the cheese powder, simply combine everything in a small blender or spice grinder and blend thoroughly. Adjust seasoning to taste. Store in a jar or tupperware.
To make mac n' cheese, boil pasta according to package instructions, but take out 1 minute before it's done so it's al dente. Then drain, return to the pot over medium low heat, along with the vegan milk, butter and cheese powder. Stir until butter melts and tapioca starch thickens, about 2-3 minutes. Serve immediately!
Notes
*A couple folks have said the onion and garlic powder at 1 tsp each is overpowering, so start with 1/2 tsp and add more as you see fit.