Melt butter in a medium sized
saucepan. If you're using fresh onion and garlic, add it to the butter and sauté. In the meantime, stir the water into the
arrowroot flour in a separate bowl, whisk well, and then whisk into the melted butter once the garlic and onion are lightly golden. Add the milk slowly and keep whisking, it should thicken a little, but not as much as when you use flour in your white sauce (also called a “roux”). Add cheese,
sea salt and pepper, and
dried garlic and onion (if you didn't use fresh) and any optional seasonings. If it looks like it's curdling a little, don't fret, mine did that too, but it comes out great in the end. Once it's mixed well, pull it off the heat and let set.