In a medium bowl, combine the flour and sugar. Add cinnamon, if desired. Slowly drizzle the butter into the bowl while stirring the crumbs with a fork. I like to start with 3-4 Tablespoons and add more as needed until the crumbs form. Do not over-mix (you do not want this to become like a dough).
Store in the refrigerator until ready to use. Evenly spread across muffins, quick breads, or pie.
