Cream together the butter and brown sugar until light and somewhat fluffy, 2-3 minutes.
Add the eggs and vanilla and mix well after each.
Whisk together the flour, baking powder, salt, and cinnamon in a separate bowl. Slowly add to the wet mixture on low until fully incorporated. Add the mini chocolate chips and fold in.
Shape into 2 10-inch by 2-inch logs on a parchment-lined or greased baking sheet. Bake for 22-23 minutes.
Remove from the oven and cool 45 minutes. Reduce the oven temperature to 300° F.
Slice the logs into ½-inch thick slices using a serrated knife. Place on baking sheet and return to the oven to bake for 15 minutes. Flip over and bake on the other side for another 15 minutes. Remove from oven and cool completely. They will become more firm as they cool. Store in an airtight container.