Preheat the oven to 425 degrees F and line a baking sheet with parchment paper (or lightly spray with oil). Measure 1/2 cup (8 tbs) vegan butter, cut into small pieces and place in the freezer for 5 minutes. You want the butter to be very cold for flaky, tall biscuits.
In a glass measuring cup, combine the soy milk and apple cider vinegar. Set aside to curdle. This is your vegan buttermilk.
Add the flour, baking powder, sugar and salt to a large mixing bowl or food processor. Whisk or pulse to combine. Now add the vegan butter pieces to the dry and either cut into the dry ingredients using a pastry cutter OR pulse several times in the processor until coarse crumbs form. If you used a food processor, dump the mixture into a large bowl.
Pour the vegan buttermilk into the bowl with the rest of the ingredients, saving a little bit for brushing on the tops (about 2 tablespoons). Gently stir until almost combined, but do not over mix. It will not be a clean ball of dough at this point, and it will be quite moist and sticky. See photos above in post for a visual reference.
Scoop the dough onto a lightly floured surface and gently work it together with your hands, shaping it into a rectangle. Flour your hands to prevent sticking, and sprinkle a little flour on the dough if it's very sticky. Just do not add too much, or the biscuits will be dry.
Gently flatten the dough into a rectangle, then fold one side into the center, then the other side. Turn the dough a half turn, and flatten again into a rectangle shape. Repeat the process two more times. This is what makes all those wonderful layers!
On the last folding, gently flatten the dough until it's about 1 inch thick. Cut into circles using a biscuit cutter, and do not twist the cutters. Try to get as many biscuits the first time. Re roll any scraps until you have 10-12 biscuits.
Arrange them so they are touching on the pan, this helps them bake up tall. Brush the tops with the remaining buttermilk and bake for 15-20 minutes, or until golden brown on top and tall. Serve warm with a dab of vegan butter and jam.
Cover any leftover biscuits and keep at room temperature for 3-4 days, or a bit longer in the refrigerator. They freeze well, too.