1/2 cup unsweetened soy milk or aquafaba
1 tablespoon lemon juice or white vinegar
1 teaspoon mustard
1/2 teaspoon salt
1 to 1 1/2 cups neutral oil
Add the soy milk or aquafaba, lemon juice or vinegar, mustard, and salt to a blender or jar
Blend or whisk until combined
Slowly drizzle in the oil while blending or whisking continuously
Continue until thick and creamy
Adjust salt, acid, or oil to taste
Refrigerate in a sealed container