Preheat the oven to 425 degrees F.
Make the vegan buttermilk by mixing the milk and vinegar in a bowl. Set aside to curdle.
In a large mixing bowl, whisk together 4 cups of flour, sugar, baking soda and salt.
Using clean fingers, work the butter into the flour mixture until it resembles coarse crumbs. Add the raisins in now, if using.
Pour in the vegan buttermilk and stir with a large wooden spoon until it's mostly together.
Knead the dough a little bit so it comes together. It won't be a perfectly round ball of dough. Add flour to the dough and your hands as needed if it's too sticky.
Transfer to a lightly floured surface and shape into a round loaf. Again, it won't look perfect! Now place the loaf onto a baking pan or better yet a cast iron pan.
Score the bread with an x using a serrated knife, about an inch to two inches deep.
Bake for 40-50 minutes, until golden. Cool for 10 minutes, then slice and enjoy.