Preheat the oven to 400°. Whisk together flour, salt, and cinnamon. Add the milk and whisk smooth. Add the eggs and whisk again. Slice the butter into tiny pieces (a little less than a teaspoon each)
Place a small piece of butter (see Cook's Note) in each muffin time and then melt the butter in the hot oven, about 2 minutes. When the butter has melted, remove from the oven and pour about 3 tablespoons of the egg mixture (I used a scant 1/4 cup size scoop) into each muffin tin.
Bake for 12 minutes, until hugely puffy and slightly browned around the edges. Remove from the oven. The pancakes will fall immediately after removing them from the oven. Use a spoon to scoop out each pancake. Sprinkle with powdered sugar, drizzle with syrup, or top with fruit. Enjoy!
Here's a tip for dividing the butter. Slice it into tablespoon amounts and then quarter each tablespoon of butter. You'll wind up with 20 small cubes of butter.