In a medium-sized pot, place the vegan butter, and let it melt over medium-low heat. Once it's melted, incorporate the rice flour, ensuring a thorough blend.
Next, introduce the soy milk, along with nutmeg, salt, and sugar, to the mixture.
Continue whisking the mixture over medium heat until it begins to thicken, which should take about 5 minutes. Make sure to whisk constantly to prevent any lumps from forming.
Reduce the heat to low and simmer the sauce for an additional 5 minutes, stirring occasionally. The sauce will continue to thicken as it cooks.
Remove the saucepan from the heat, and taste the sauce. Add salt according to your preference, and whisk it in until well incorporated.
Allow the Vegan Béchamel Sauce to cool for a few minutes before using it. It will thicken further as it cools.
Once cooled, the sauce is ready to be used in your favorite recipes. It's a versatile sauce that can be used in lasagnas, gratins, pasta dishes, and more.
Notes
If the sauce becomes too thick, you can add a little more soy milk to thin it out. Similarly, if it's too thin, you can return it to the heat and cook for a few more minutes to thicken it further.