Preheat the oven to 390 degrees.
Coat each of the holes in a muffin tin liberally with butter.
In a large bowl, whisk together the flour, baking powder, salt, and cinnamon.
Grate the cold butter into the flour mixture and cut the butter into the flour using forks or a pastry cutter. Work the mixture together until the butter is in little pea sized clumps, and mixed well throughout.
Slowly pour the milk into the dough, and mix it with a fork, or using your hands as needed to incorporate the dough together well. (Add a little more flour, or a little more milk as needed)
Form the dough into a ball and let rest for a few minutes.
Lightly flour your surface and fold the dough over onto itself 3 or 4 times. Allow to rest for a second time for another few minutes.
Then roll the out into a rectangle about 18 x 14 inches or until the dough is about 1/8 to 1/4 inch thick.
Spread the melted butter from the cinnamon filling all over the dough, leaving about 1/2 inch around the edges.
Combine the brown sugar and cinnamon in a small bowl. Then sprinkle the cinnamon sugar mixture all over the dough.
Starting with the longest edge of the dough, roll your dough up as tightly as you can.
Cut the dough into 12 equal sized rolls.
Pinch the bottom of each roll together and then place them into each of the prepared muffin tin spots.
Bake for 15 to 25 minutes until golden brown and the center is done.