Preheat the oven to 450 degrees F. Line a baking sheet with parchment paper.
Cut 1 stick (1/2 cup) butter into cubes. Place back in the refrigerator to chill. Melt the remaining 1/4 cup butter in the microwave or on the stovetop. Allow it to cool to just above room temperature.
Place the flour, brown sugar, baking powder, cinnamon, and salt in a food processor. Pulse to combine. Then add the cold butter cubes, and pulse until the cubes are cut down to pea-size pieces.
Add the buttermilk and vanilla extract. Pulse until the mixture comes together into a smooth ball.
While the dough is still cold, use a 3-tablespoon scoop to measure out 14 biscuits. Arrange them on the baking sheet with room to spread a little.
Quickly brush the melted butter over the tops and place in the oven. Bake for 10-12 minutes, until golden around the edges.
Sprinkle the tops with extra cinnamon, if desired. Serve warm, or within 2 hours.
For convenience, you can prep the dough up to a day ahead and place it in the refrigerator. When ready to bake, preheat the oven and portion the dough out onto baking sheets.