Add in eggs one at a time then, add milk and mix until combined.
2 large eggs, ¾ cup milk
Stir in the dry ingredients and mix until well incorporated (do not overmix the batter).
Spoon 2 tablespoons of batter into each muffin cup and top with ¼ teaspoon of the cinnamon sugar swirl; add two more layers of the cake batter and cinnamon swirl (make the top layer of the cake batter).
Bake for 15-20 minutes, remove from the oven and place on a cooling rack to cool.
Make the frosting
In a mixing bowl, beat the whipping cream, powdered sugar, cinnamon and vanilla extract until smooth and stiff peak forms.
1 ¼ cups heavy whipping cream, 1 teaspoon ground cinnamon, 1 teaspoon vanilla extract, ½ cup powdered sugar
Add the frosting in a piping bag and pipe on top of the cupcakes, sprinkle with some cinnamon sugar swirl.
Notes
Before I start with this recipe, I like to set aside all ingredients beforehand to be at room temperature when preparing the batter because eggs and butter should be at room temperature for better results.