There are multiple ways to make a decent vegan white sauce. Soy milk (or similar) thickened with roux or xanthan gum or rice flour or cornstarch or by blending with silken tofu or cooked rice or cooked cauliflower; and those are just a few. Here is an example of a bechamel. It gets real thick quickly but I use it when making vegan mac & cheese so I want it thick. It is easy enough to thin it once done with more soy milk.
Vegan Bechamel Sauce
Weight or Volume Ingredients
1 cup sunflower oil
10 tablespoons rice flour
6 cups soy milk
1 pinch nutmeg
to taste salt
to taste black pepper
Procedure:
Heat sunflower oil over low heat and stir in rice flour. Continue to stir and cook on low heat for 5 minutes. Add soy milk and nutmeg. turn heat to high and bring up to boil while continuing to stir. Once it comes to a boil, check consistency as it will probably be thickened enough. Turn heat off and season with salt and pepper.
Vegan Bechamel Sauce
Weight or Volume Ingredients
1 cup sunflower oil
10 tablespoons rice flour
6 cups soy milk
1 pinch nutmeg
to taste salt
to taste black pepper
Procedure:
Heat sunflower oil over low heat and stir in rice flour. Continue to stir and cook on low heat for 5 minutes. Add soy milk and nutmeg. turn heat to high and bring up to boil while continuing to stir. Once it comes to a boil, check consistency as it will probably be thickened enough. Turn heat off and season with salt and pepper.