Preheat the oven to 450 F and line a baking sheet with parchment paper.
In a small bowl, combine 1 cup soy milk with the vinegar and let sit for 10 minutes.
In a large bowl, combine 2 ½ cups flour, baking powder, baking soda, and ½ teaspoon salt. Add the butter and mix it into the dough with your hands until crumbly.
Create a well in the center of the flour and butter mixture. Add the milk and vinegar mixture, stir with a wooden spoon, and form the dough into a ball.
Place the dough ball on a floured work surface and roll out to ½ to ¾ inch thick. Cut out 10 circles, about 3-inches across, with a cup or round cookie cutter. Place the biscuits on the prepared baking sheet and bake for 12 minutes until the tops are golden brown.
Meanwhile, to make the gravy, add the oil to a large skillet and heat to medium-high. Crumble in the tempeh and add the soy sauce, Worcestershire, oregano, fennel seeds, garlic granules, onion powder, paprika, sage, and remaining salt. Cook for 5 minutes, stirring frequently, then add the water and reduce the heat to medium. Cook for 10 more minutes.
Add the remaining ⅓ cup flour to the pan and stir to coat the tempeh. Add in the remaining soy milk, lower heat to medium-low, and cook, stirring every so often, for 5-10 minutes until the gravy has thickened.
Pour the gravy over the biscuits and garnish with chopped chives, if desired, before serving.