Cinnamon Roll Pancakes

¼ cup packed brown sugar
5 tbsp melted butter, plus pats for serving
3 tbsp plus 1 cup flour
1 ½ tsp cinnamon
¾ cup milk
2 tbsp white vinegar
2 tbsp white sugar
1 tsp baking powder
½ tsp baking soda
½ tsp salt
1 egg
1 ½ tsp vanilla extract
Cream cheese icing: Stir together ¼ cup softened butter and 2 oz softened cream cheese in a microwave-safe bowl; microwave 40 seconds. Stir until smooth. If necessary, continue microwaving and stirring at 10-second intervals until completely melted. Stirr in ¾ cup powdered sugar and ½ tsp vanilla extract. Makes ⅔ cup.

For cinnamon filling: Stir together brown sugar, 3 tbsp melted butter, 3 tbsp flour, and the cinnamon in a small bowl. Pour into a 1-qt zip-top plastic bag. Freeze until firm enough to pipe, about 5 minutes.
Meanwhile, for pancakes: Stir together milk and vinegar in a bowl; let stand until milk thickens, about 5 minutes. In another bowl, stir together white sugar, baking powder, baking soda, salt, and remaining 1 cup flour. Whisk egg, vanilla, and remaining 2 tbsp melted butter into milk mixture. SLowly pour milk mixture into flour mixture, whisking constantly, until batter is just moistened and evenly mixed. (Some small lumps are fine.)
Snip off the corner of the zip-top bag with cinnamon filling. Heat a griddle or skillet over medium heat and lightly coat with cooking spray. Pour ¼ cup batter into the center of griddle. Cook pancake until bubbles start to appear, 2 to 3 minutes. Pipe a spiral swirl of cinnamon filling onto the pancake.
Flip and cook until other side of pancake is lightly browned, 2 to 3 minutes. Repeat with remaining ingredients, wiping griddle with a cloth and coating it with additional cooking spray between each pancake. Serve, swirl side up, topped with butter pats and drizzle with Cream Cheese Icing.