Cut your butter into small cubes and chill in the freezer for 10-15 minutes to ensure the biscuit has the best flaky layers.
Preheat oven to 425°.
Melt your 2 tablespoons of butter and mix it together with the brown sugar and cinnamon until it forms a paste. Set aside.
In the bowl of a food processor, combine the dry biscuit ingredients (flour, baking powder, sugar and salt). Cut in the frozen butter until it forms a coarse crumb dough. Add in the milk and mix until just combined.
On a lightly floured surface, roll the dough together until it forms a cohesive ball. Fold the dough in half 5-6 times, rotation 90° between each fold.
Gently roll out the dough ball into a 9x12 inch rectangle and evenly spread the butter and sugar mixture over the top of the dough.
Roll the dough into a cylinder along the long side. Cut the roll into 8 equal pieces and place in a greased baking pan or pie sheet.
Bake at 425° for 18-22 minutes - until fully cooked and the edges have browned slightly. Remove the biscuits to a wire rack to cool.
While the cinnamon biscuits are baking, whisk all the icing ingredients together until fully combined. Set aside.
Once the biscuits are fully cooled, drizzle them with the icing. Enjoy immediately or store in a Tupperware in the fridge for up to 3 days. Reheat in the microwave for 15 seconds before eating for the best taste.