Heat oven to 350°F Place paper baking cups into muffin pan cups; set aside.
Combine all filling ingredients in medium bowl. Beat at medium speed until creamy; set aside.
Combine boiling water and tea bags in glass measuring cup, let stand 5 minutes. Remove tea bags, squeezing out excess liquid. Add enough water, if necessary, to equal 1 1/2 cups.
Reserve 3 tablespoons prepared tea; set aside. Place remaining prepared tea in large bowl; add cake mix, melted butter and eggs. Beat at low speed 30 seconds. Beat at medium speed, scraping bowl often, until creamy.
Spoon about 2 tablespoons cake batter into each prepared muffin cup. Top each with 1 tablespoon filling. Spoon additional cake batter over filling until cups are about 2/3 full. (DO NOT OVERFILL.) (Batter does not have to cover filling completely.) Bake for 19 to 22 minutes or until toothpick inserted comes out clean. Cool completely.
Combine 3 tablespoons reserved prepared tea and milk in 2-quart saucepan. Add flour and cocoa; whisk until smooth. Cook over medium heat, stirring constantly, until mixture thickens and just comes to a boil (4 to 6 minutes). Remove from heat; cool about 15 minutes.
Combine 1 cup butter, 1 cup sugar and cinnamon in medium bowl. Beat at high speed until creamy. Continue beating, gradually adding cocoa mixture, 1 tablespoon at a time, until light and creamy and sugar is dissolved. Frost or pipe cooled cupcakes. Sprinkle with cinnamon, if desired. Store refrigerated.