Pre-heat oven to 350 degrees and line a cupcake tin with 12 papers.
In the bowl of a stand mixer or in a large bowl with a hand mixer, cream together butter and sugar on medium-high speed until light and fluffy, about 3 minutes.
Add eggs in one at a time, mixing well after each addition. Mix in vanilla and peppermint extracts.
In a separate medium bowl, whisk together flour, cocoa powder, baking soda, and salt.
With mixer on low speed, mix in dry ingredients in 2 additions, alternating with milk. Mix in each addition until just incorporated. Gently fold in chocolate chips.
Fill cupcake liners about ¾ of the way with batter. Bake cupcakes for 18-20 minutes, until toothpick inserted into center comes out clean.
Let cupcakes cool in tin for 5 minutes before moving to wire racks to cool completely.
Frost cupcakes with Bailey's frosting. I used a pastry bag and Wilton 1A pastry tip for mine. Top with additional chocolate chips, if desired.