Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the flour, baking powder, salt, and sugar. Whisk until well mixed.
Cut in the cold butter until the mixture resembles coarse crumbs.
Make a well in the center, add the buttermilk, and stir gently until just combined.
Turn the dough out onto a floured surface and gently knead it 4-5 times. Shape into a 3/4 inch thick circle.
Cut out biscuits and arrange them on the baking sheet. Bake for 12-15 minutes until golden.
While the biscuits are baking, prepare the chocolate gravy by whisking together sugar, cocoa, flour, and salt in a saucepan.
Gradually whisk in the milk until the mixture is smooth. Cook over medium heat, whisking constantly until the gravy thickens.
Remove from heat and stir in butter and vanilla until melted.
Serve the biscuits warm with generous amounts of chocolate gravy over them.