To begin, preheat your oven to 425 and line a muffin pan with 10 cupcake liners (or spray with non-stick spray).
To a medium sized mixing bowl, add your flour, cinnamon, baking soda and salt and stir them together.
In a microwave safe bowl, add your milk and microwave till warm. Add your espresso powder to your milk and whisk it in till it's well combined.
In a large sized mixing bowl, add your butter and sugar and blend them together with a beater for a couple minutes, or till they're creamy. Add your eggs and espresso milk and blend together again, till combined.
Pour your dry ingredients into your large bowl of wet ingredients. Stir everything together till you have a thick muffin batter. Gently fold in your chocolate chips, if using.
Fill your muffin cavities to the top with muffin batter. Bake in the oven for 5 minutes. Then, reduce your oven temperature to 350 and bake for another 17-19 minutes, or till the tops are springy to touch and a toothpick inserted comes out clean.
Let cool. Devour!
Stored in an airtight container these muffins last about 4-5 days on the counter, or a week in the fridge.