Center a rack in the oven and preheat the oven to 400 degrees F. Butter or spray 12 cupcake cavities in a regular-size pan or fit with paper cups. Place the pan on a baking sheet.
Whisk together the flour, baking powder, baking soda, salt and spices. Set aside.
Working with a stand mixer fitted with a paddle attachment or with a hand mixer in a large bowl, beat the butter at medium speed until soft. Add both the sugars and continue to beat until light and smooth.
One by one, add the eggs, beating for a minute after they are incorporated, then beat in the vanilla.
Lower the mixer speed and mix in the pumpkin and buttermilk. Add the dry ingredients in a steady stream, mixing only until they disappear. To avoid overmixing, you can stop the machine early and stir in any remaining dry ingredients into the batter using a rubber spatula.
Stir in the raisins and 1/2 cup of the chocolate chips. Divide the batter evenly among the cupcake cavities. Using the remaining 1/4 cup chocolate chips, dot the top of each muffin.
Bake for about 17-20 minutes, or until a knife inserted into the center of the muffins comes out clean.
Transfer the pan to a rack and cool the muffins for 5 minutes in the pan, then carefully remove each one from its cavity to finish cooling on the rack.
Notes
Raisins add subtle sweetness and a little bit of texture to these muffins. However, you can omit them if desired or even substitute them with a few extra chocolate chips or chopped nuts such as walnuts or pecans.
Be sure to use unsweetened pumpkin puree for these muffins, not pumpkin pie filling. The pumpkin puree lends a ton of moisture.
Use the scoop and sweep method to measure your flour to avoid dense, crumbly muffins. To do so, aerate the flour with a spoon. Then, scoop the flour into a measuring cup until overflowing. Gently scrape the excess with the back end of a butter knife to level. Never pack down your flour by tapping the cup on a hard surface or scooping straight from the bag.
This recipe uses ground cinnamon, nutmeg, freshly grated ginger, and allspice. Their flavor is subtle and not overpowering in the finished muffins. Optionally add a little extra if you want their flavors to be more potent.
These muffins will keep well in an air-tight container or zip-top bag kept at room temperature for 3-4 days. You can also store them in the refrigerator (covered/sealed) for 1 week.
TO FREEZE - Place the muffins in a large ziptop bag or in an air-tight container and store in the freezer for up to 3 months. Thaw at room temperature.