In a stand mixer or using a handheld mixer, cream butter and sugars until pale and creamy. Add eggs 1 at a time and beat for 30 seconds after adding each one and for another minute until well incorporated. Use a spatula to scrape down the sides if necessary.
Add vanilla and mix in.
Whisk together flour, cocoa powder, baking powder, baking soda & salt in a separate bowl.
Add the flour mixture to the batter start to combine. Add the Bailey & milk to the batter and beat on low-medium speed until completely combined.
Scoop the batter into lined muffin tins and bake at 180 degrees C for 15-18 minutes until a toothpick inserted comes out clean.
Place cupcakes on a cooling rack and allow to cool completely before frosting.
Add Baileys & chocolate chips to a Pyrex jug or over a double boiler on the stove. Either microwave or simmer until the chocolate has totally melted. Stir it together so that it is smooth and allow to cool slightly before spreading onto the cupcakes.
Add all ingredients to the bowl of a stand mixer and beat on high speed for 4-5 minutes until frosting is fluffy.
Using a piping bag or a knife, pipe or spread the frosting onto the cupcakes on top of the ganache. Sprinkle with chocolate sprinkles.