Preheat oven to 450 degrees and line a baking sheet with parchment paper.
Measure out just under one cup of soy milk. To be exact, 3/4 cups plus 3 Tbsp. Then briskly stir the 2 Tbsp lemon juice into the milk. Set this mixture aside for a few minutes to allow it to thicken.
While the 'buttermilk' thickens, add the flour, salt, baking soda and baking powder to a large mixing bowl. Stir to combine.
Remove the vegan butter from the fridge - so that it is as cold as can be - and measure out six tablespoons. Plop the vegan butter into the mixing bowl. Using your pastry cutter, cut the butter into the flour. You want tiny bits so that the flour is lumpy and the butter combined into the mix. You don't want to overwork the butter to melt it - just cut briskly to get it into little chilled bits. This flour mixture will be lumpy from the butter.
Give your vegan buttermilk a brisk stir. Measure out one cup and pour into the center of the flour bowl. Using a large spoon - I like to use a wooden spoon - gently stir to combine the liquid and the flour. Fold just until you have a nice lumpy, wet dough and there is no more dry flour to be seen.
Sprinkle a generous amount of flour on your work surface. Then plop the dough on top. Sprinkle a light dusting of flour over the dough. Pat down the dough to about 1/2 inch thick, then fold the dough over a few time and pat down again - to about 1/2 - 1 inch - depending on how tall you want your biscuits. Note: Thicker biscuits will yield a smaller quantity.
Cut your biscuits out with a 2" biscuit cutter. Cut by pushing down and pulling straight up - no twisting. transfer biscuit to baking sheet. Repeat until all the dough is used up. You will need to reform the dough a few times before using all of it. Optional: Melt the additional tablespoon of butter and brush tops of biscuits with it, using a pastry brush. Warning, this really bumps up the "buttery" flavor so use with caution! I actually don't prefer the extra butter tops, but it does create a smoother top with nice browning too. Tip: Try doing half and half your first batch and see what you prefer.
Place the biscuits in the 450 degree oven. Bake for 10-15 minutes - depending on size and how browned you like the edges. As soon as you see slight browning on the edge the biscuits are done. Add a few minutes if you like slightly crispy tops and bottoms. Or remove promptly for softer edges.
Serve right away or store in the fridge, in a sealed bag or container, for up to two days. For longer storage, store in the freezer.