Preheat oven to 175°C and line a 12 hole patty pan tray with cupcake papers.
Sift all dry ingredients into a mixing bowl. Then using the stand mixer fitted with the paddle attachment, place the dry ingredients into the mixer and at low speed start adding one butter cube at a time until all incorporated.
Keeping the mixer speed on low, add one egg at a time. Add vanilla extract to milk. Then with mixer speed continuing on low, add milk slowly until all incorporated. Be careful not to flood the batter.
Scrape down the sides of the bowl and paddle then resume mixing on medium-high speed for 30 seconds ensuring the batter is smooth. Then fill cupcake papers ⅔ full and bake for 17-21 minutes until light golden in colour. Transfer to a wire rack and allow to cool completely.
Heat the milk over the stove to 60°C then add the loose chai tea and let it brew for 10 minutes. Once brewed using a tea strainer, strain the milk infused with chai and set aside to cool down to room temperature.
Using the stand mixer fitted with the paddle attachment, cream the butter on medium speed. Then add the dry spices and vanilla extract and mix on medium speed until combined.
Gradually add the icing sugar (½ a cup at a time) and beat until fully incorporated on medium. Then add the milk and beat on high speed until the mixture is smooth and fluffy, not too thick.
Pipe the frosting onto the cupcakes as desired and sprinkle with cinnamon (optional).