Whisk together the flour, baking soda, and pumpkin pie spice.
In a separate bowl, whisk together the pumpkin, melted butter, vanilla extract, brown sugar, milk, and eggs.
Add the dry ingredients to the wet, and mix until just combined. Do not over mix.
Fold in the mini chocolate chips using a rubber spatula.
Spray a mini muffin tin with olive oil cooking spray.
Distribute the muffin batter into the 24 mini muffin cups using a mini cookie scoop.
Bake the mini pumpkin muffins at 350 degrees for 15-18 minutes, or until a toothpick inserted comes out clean.
Cool the muffins for 2-3 minutes in the pan, then use a butter knife to gently remove them onto a wire cooling rack to cool completely.