Melt the butter, brown sugar, and milk together in a bowl in the microwave for 30 seconds. (Cover bowl, in case it splatters.) Alternately melt ingredients together in a small saucepan on the stovetop. Then remove from heat.
Once the butter is melted, whisk until the brown sugar dissolves.
Add powdered sugar and cinnamon. Whisk until smooth. Cool slightly.
Pour, spoon, spread, or drizzle the cinnamon brown sugar glaze onto the desired dessert and allow time for glaze to set.
Notes
YIELD: Approximately 2/3 cup of glaze. One serving is about 3/4 Tablespoon.