Pre-heat your oven to 400° F, and either grease a baking sheet, or add parchment paper to it. I prefer to use parchment paper because the scones just slide right off of it after baking.
Whisk Bisquick baking mix, sugar, and cinnamon together in a large mixing bowl.
Using a pastry blender (or table knife), cut the cold, sliced butter into the dry ingredients until the mixture consists of fine crumbles.
In a separate measuring cup or bowl, beat the egg, vanilla extract, and buttermilk together.
Mix the egg mixture into the dry ingredients, just 'til blended. Be careful not to overmix.
Drop the dough, by spoonfuls, onto your parchment paper covered baking sheet.
Brush the top of each scone with buttermilk.
Then sprinkle a little cinnamon sugar on top of each scone.
Bake your scones at 400° F for 12 to 15 minutes, or 'til they turn a nice golden brown. They're best served while warm with butter, apple butter, etc.