1. Preheat oven to 450F and grease a muffin pan. Stir pancake mix, sugar, cinnamon, and 2/3 cup milk together. Spoon dough into muffin pan; there should be about 8 buns. Bake in oven for 8 to 10 minutes.
2. While the buns are baking, melt butter in the microwave. Pour 1/6 cup of milk and the powdered sugar on top of the butter. Beat for about 30 seconds by hand. Add vanilla and beat about 5 seconds.
3. When buns are ready, immediatly take out of the oven and spoon frosting over. Dust with cinnamon.