Add in the egg, and mix until combined.
Add in buttermilk, vanilla extract and melted butter. Mix until just combined.
Lastly, add in the pumpkin puree and mix until just combined.
Drop about 1 Tbsp of batter into each mini muffin cup.
*Alternatively, you could substitute pumpkin pie spice for these spices. If substituting, I suggest using 1/2 tsp cinnamon + 1 tsp pumpkin pie spice.